IGNITION 
DEVICES 

FOR  MOTORS 

NEW  AND  ENLARGED  EDITION 


S-R-BOTTONE 


HANDICRAFT   SERIES. 

A  Series  of  Practical  Manuals. 

Edited    by  PAUL    N.   HASLUCK,   Editor  of  "Work,"  "Technical  Instru 

Q^-Loc  "   ~+~ 


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Reviving, 
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iver.     Buil 
Tricycle, 
ings  and  A< 
g.     Repair 
igs  and  Diai 
•rnament. 
>rnament. 
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je  Frame  Ci 
OTOunting    Pi' 
Plush   and    Cork.     Hangir 


Making    Oxford    Frames.     Gilding  Picture   Frames. 
Making  Photograph  Frames.     Frames  covered  with 
Packing  Pictures. 
Smiths'  Work.     With  211  Engravings  and  Diagrams. 

Contents.— Forges  and  Appliances.     Hand  Tools.     Drawing  Down    and  Up-s 
Welding  and  Punching.     Conditions  of  Work:  Principles  of  Formation.     Bendu 
Ring  Making.     Miscellaneous  Examples  of  Forged  Work.     Cranks,  Model  Wor 
Die  Forging.     Home-made  Forges.     The  Manipulation  of  Steel  at  the  t  orge. 
Glass  Working  by  Heat  and  Abrasion.     With  300  Engravings  and  Diagrai 

Contents. — Appliances  used_in  Glass  ^Blowing.     Manipulating  Glass  Tubing. 
Bulbs  and  Flasks. 
Etching  Glass  Fancy 

Glass  Apparatus;  Boring ._, «,    ,__, 

Specula.     Turning,  Chipping,  and  Grinding  Glass.     The  Manufacture  of  Glass. 

DAVID  McKAY,  Publisher,  Washington  Square,  Philadelphia. 


HANDICRAFT  SERIES   (Continued]. 


ilding  Model  Boats.     With  168  Engravings  and  Diagrams. 

Contents. — Building  Model  Yachts.  Rigging  and  Sailing  Model  Yachts.  Making  and 
ting  Simple  Model  Boats.  Building  a  Model  Atlantic  Liner.  Vertical  Engine,  for  a 
del  Launch.  Model  Launch  Engine  with  Reversing  Gear.  Making  a  Show  Case  for 
lodel  Boat. 

ectric  Bells,  How  to  Make  and  Fit  Them.  With  162  Engravings  and  Diagrams. 
Contents. — The  Electric  Current  and  the  Laws  that  Govern  it.  Current  Conductors 
id  in  Electric-Bell  Work.  Wiring  for  Electric  Bells.  Elaborated  Systems  of  Wiring; 
irglar  Alarms.  Batteries  for  Electric  Bells.  The  Construction  of  Electric  Bells,  Pushes, 
d  Switches.  Indicators  for  Electric-Bell  Systems. 

imboo  Work.     With  177  Engravings  and  Diagrams. 

Contents. — Bamboo:  Its  Sources  and  Uses.  How  to  Work  Bamboo.  Bamboo  Tables. 
,mboo  Chairs  and  Seats.  Bamboo  Bedroom  Furniture.  Bamboo  Hall  Racks  and  Stands, 
.mboo  Music  Racks.  Bamboo*  Cabinets  and  Bookcases.  Bamboo  Window  Blinds, 
scellaneous  Articles  of  Bamboo.  Bamboo  Mail  Cart. 

ixidermy.     With  108  Engravings  and  Diagrams. 

Contents. — Skinning  Birds.  Stuffing  and  Mounting  Birds.  Skinning  and  Stuffing 
immals.  Mounting  Animals'  Horned  Heads:  Polishing  and  Mounting  Horns.  Skin- 
3g,  Stuffing,  and  Casting  Fish.  Preserving,  Cleaning,  and  Dyeing  Skins.  Preserving 
sects,  and  Birds'  Eggs.  Cases  for  Mounting  Specimens. 

liloring.     With  180  Engravings  and  Diagrams. 

Contents. — Tailors'  Requisites  and  Methods  of  Stitching.  Simple  Repairs  and  Press- 
;.  Relining,  Repocketing,  and  Recollaring.  How  to  Cut  and  Make  Trousers.  How 
Cut  and  Make  Vests.  Cutting  and  Making  Lounge  and  Reefer  Jackets.  Cutting  and 
aking  Morning  and  Frock  Coats. 

lotographic  Cameras  and  Accessories.      Comprising  How  TO  MAKE  CAMERAS, 

DARK  SLIDES,  SHUTTERS,  and  STANDS.     With  160  Illustrations. 

Contents. — Photographic  Lenses  and  How  to  Test  them.  Modern  Half-plate  Cameras, 
and  and  Pocket  Cameras.  Ferrotype  Cameras.  Stereoscopic  Cameras.  Enlarging 
imeras.  Dark  Slides.  Cinematograph  Management. 

ptical  Lanterns.     Comprising  THE  CONSTRUCTION  AND  MANAGEMENT  OF   OPTICAL 

LANTERNS  AND  THE  MAKING  OF  SLIDES.     With  160  Illustrations. 

Contents. — Single  Lanterns.  Dissolving  View  Lanterns.  Illuminant  for  Optical  Lan- 
rns.  Optical  Lantern  Accessories.  Conducting  a  Lime-light  Lantern  Exhibition.  Ex- 
iriments  with  Optical  Lanterns.  Painting  Lantern  Slides.  Photographic  Lantern 
ides.  Mechanical  Lantern  Slides.  Cinematograph  Management. 

ngraving  Metals.     With  Numerous  Illustrations. 

Contents. — Introduction  and  Terms  used.  Engravers'  Tools  and  their  Uses.  Ele- 
entary  Exercises  in  Engraving.  Engraving  Plate  and  Precious  Metals.  Engraving 
onograms.  Transfer  Process  of  Engraving  Metals.  Engraving  Name  Plates.  En- 
aving  Coffin  Plates.  Engraving  Steel  Plates.  Chasing  and  Embossing  Metals.  Etch- 
g  Metals. 

asket  Work.     With  189  Illustrations. 

Contents. — Tools  and  Materials.  Simple  Baskets.  Grocer's  Square  Baskets.  Round 
iskets.  Oval  Baskets.  Flat  Fruit  Baskets.  Wicker  Elbow  Chairs.  Basket  Bottle- 
sings.  Doctors'  and  Chemists'  Baskets.  Fancy  Basket  Work.  Sussex  Trug  Basket, 
iscellaneous  Basket  Work.  Index. 

ookbinding.     With  125  Engravings  and  Diagrams. 

Contents. — Bookbinders'  Appliances.  Folding  Printed  Book  Sheets.  Beating  and 
jwing.  Rounding,  Backing,  and  Cover  Cutting.  Cutting  Book  Edges.  Covering 
Doks.  Cloth-bound  Books,  Pamphlets,  etc.  Account  Books,  Ledgers,  etc.  Coloring, 
Drinkling,  and  Marbling  Book  Edges.  Marbling  Book  Papers.  Gilding  Book  Edges, 
jrinkling  and  Tree  Marbling  Book  Covers.  Lettering,  Gilding,  and  Finishing  Book 
>vers.  Index. 

ent  Iron  Work.     Including  ELEMENTARY  ART  METAL  WORK.     With  269  Engravings 

and  Diagrams. 

Contents. — Tools  and  Materials.     Bending  and  Working  Strip  Iron.     Simple  Exercises 
Bent  Iron.     Floral  Ornaments  for  Bent  Iron  Work.     Candlesticks.     Hall  Lanterns. 
;reens,  Grilles,   etc.     Table   Lamps.     Suspended  Lamps  and  Flower  Bowls.     Photo- 
•aph  Frames.     Newspaper  Rack.     Floor  Lamps.     Miscellaneous  Examples.     Index. 

holography.     With  Numerous  Engravings  and  Diagrams. 

Contents. — The  Camera  and  its  Accessories.     The  Studio  and  the  Dark  Room.     Plates. 


sposure.     Developing  and  Fixing  Negatives.     Intensification  and  Reduction  of  Nega- 
tes.    Portraiture  and    Picture   Composition.     Flash-light    Photography.     Retouching 
sgatives.     Processes  of   Printing  from    Negatives.     Mounting  and    Finis" 
>pying  and  Enlarging.     Stereoscopic  Photography.     Ferrotype  Photoerap! 

DAVID  McKAY,  Publisher,  Washington  Square,  Philadelphia. 


HANDICRAFT  SERIES  (Continued^. 


Upholstery.     With  162  Engravings  and  Diagrams. 

Contents. — Upholsterers'  Materials.  Upholsterers'  Tools  and  Appliances.  Webbing, 
Springing,  Stuffing,  and  Tufting.  Making  Seat  Cushions  and  Squabs.  Upholstering  an 
Easy  Chair.  Upholstering  Couches  and  Sofas.  Upholstering  Footstools,  Fenderettes, 
etc.  Miscellaneous  Upholstery.  Mattress  Making  and  Re  pah  ing.  Fancy  Upholstery. 
Renovating  and  Repairing  Upholstered  Furniture.  Planning  and  Laying  Carpets  and 
Linoleum.  Index. 

Leather  Working.     With  162  Engravings  and  Diagrams. 

Contents. — Qualities  and  Varieties  of    Leather.     Strap  Cutting  and  Making.     Letter 

Cases  and  Writing  Pads.     Ha4r  Brush  and  Collar  Cases.     Hat  Cases.     Banjo  and  Man- 

•    doline  Cases.     Bags.     Portmanteaux  and  Travelling  Trunks.     Knapsacks  and  Satchels. 

Leather   Ornamentation.      Footballs.      Dyeing   Leather.      Miscellaneous    Examples    of 

Leather  Work.     Index. 

Harness  Making.     With  197  Engravings  and  Diagrams. 

Contents.— Harness  Makers'  Tools.  Harness  Makers'  Materials.  Simple  Exercises  in 
Stitching.  Looping.  Cart  Harness.  Cart  Collars.  Cart  Saddles.  Fore  Gear  and  Leader 
Harness.  Plough  Harness.  Bits,  Spurs,  Stirrups,  and  Harness  Furniture.  Van  and  Cab 
Harness.  Index.  -.•  « 

Saddlery.     With  99  Engravings  and  Diagrams. 

Contents. — Gentleman's  Riding  Saddle.  Panel  for  Gentleman's  Saddle.  Ladies'  Side 
Saddles.  Children's  Saddles  or  Pilches.  Saddle  Cruppers,  Breastplates,  and  other 
Accessories.  Riding  Bridles.  Breaking-down  Tackel.  Head  Collars.  Horse  Clothing. 
Knee-caps  and  Miscellaneous  Articles.  Repairing  Harness  and  Saddlery.  Re-lining 
Collars  and  Saddles.  Riding  and  Driving  Whips.  Superior  Set  of  Gig  Harness.  Index. 

Knotting  and  Splicing,  Ropes  and  Cordage.  With  208  Engravings  and  Diagrams. 
Contents. — Introduction.  Rope  Formation.  Simple  and  Useful  Knots.  Eye  Knots, 
Hitches  and  Bends.  Ring  Knots  and  Rope  Shortenings.  Ties  and  Lashings.  Fancy 
Knots.  Rope  Splicing.  Working  Cordage.  Hammock  Making.  Lashings  and  Ties  for 
Scaffolding.  Splicing  and  Socketing  Wire  Ropes.  Index. 

Beehives  and  Beekeepers'  Appliances.     With  155  Engravings  and  Diagrams. 

Contents. — Introduction.  A  Bar-Frame  Beehive.  Temporary  Beehive.  Tiering  Bar- 
Frame  Beehive.  The  "  W.  B.  C."  Beehive.  Furnishing  and  Stocking  a  Beehive.  Obser- 
vatory Beehive  for  Permanent  Use.  Observatory  Beehive  for  Temporary  Use.  Inspection 
Case  for  Beehives.  Hive  for  Rearing  Queen  Bees.  Super-Clearers.  Bee  Smoker. 
Honey  Extractors.  Wax  Extractors.  Beekeepers'  Miscellaneous  Appliances.  Index. 

Electro-Plating.     With  Numerous  Engravings  and  Diagrams. 

Contents.— Introduction.  Tanks,  Vats,  and  other  Apparatus.  Batteries,  Dynamos, 
and  Electrical  Accessories.  Appliances  for  Preparing  and  Finishing  Work.  Silver- 
Plating.  Copper-Plating.  Gold-Plating.  Nickel-Plating  and  Cycle-Plating.  Finishing 
Electro-Plated  Goods.  Electro-Plating  with  Various  Metals  and  Alloys.  Index. 

Clay  Modelling  and  Plaster  Casting.     With  153  Illustrations. 

Contents. — Drawing  for  Modellers.  Tools  and  Materials  for  Clay  Modelling.  Clay  Model- 
ling. Modelling  Ornament.  Modelling  the  Human  Figure.  Waste-Moulding  Process  of 
Plaster  Casting.  Piece-Moulding  and  Gelatine-Moulding.  Taking  Plaster  Casts  from 
Nature.  Clay  Squeezing  or  Clay  Moulding.  Finishing  Plaster  Casts.  Picture  Frames 
in  Plaster.  Index. 

Violins  and  other  Stringed  Instruments.     With  about  180  Illustrations. 
v  Contents. — Materials    and    Tools   for  Violin  Making.     Violin  Moulds.     Violin    Making. 

Varnishing  and  Finishing  Violins.  Double  Bass  and  a  Violoncello.  Japanese  One-string 
Violin.  Mandolin  Making.  Guitar  Making.  Banjo  Making.  Zither  Makin<».  Dulcimer 
Making.  Index. 

Glass  Writing,  Embossing,  and  Fascia  Work.     (Including  the  Making  and  Fixing 

of  Wood  Letters  and  Illuminated  Signs.)     With  129  Illustrations. 

Contents. — Plain  Lettering  and  Simple  Tablets.  Gold  Lettering.  Blocked  Letters. 
Stencil  Cutting.  Gold  Etching.  Embossing.  French  or  Treble  Embossing.  Incised 
Fascias,  Stall-plates,  and  Grained  Background.  Letters  in  Perspective;  Spacing  Letters. 
Arrangement  of  Wording  and  Colors.  Wood  Letters.  Illuminated  Signs.  Temporary 
Signs  for  Windows.  Imitation  Inlaid  Signs.  Imitation  Mosaic  Signs.  Specimen  Alpha- 
bets. Index. 

Photographic  Chemistry.     With  31  Engravings  and  Diagrams. 

Contents. — Introductory:  Relation  of  Chemistry  to  Photography.  Some  Fundamental 
Chemical  Laws.  Meaning  of  Symbols  and  Equations.  Water :  Its  Properties  and 
Impurities.  Oxygen  and  Hydrogen  Photographically  Considered.  Theories  Concerning 
the  Latent  Image.  Chemistry  of  Development,  Toning,  Intensification,  etc.  Nitrogen 
Compounds  Employed  in  Photography.  The  Halogens  and  Haloid  Salts.  Sulphur  and 
its  Compounds.  Metals,  Alkali  Metals,  etc.  Organic  or  Carbon  Compounds  used  in 
Photography.  Pyroxyline,  Albumen,  Gelatine,  etc.  Benzene  and  the  Organic  Developers. 
Index* 

DAVID  McKAY,  Publisher,  Washington  Square,  Philadelphia. 


IGNITION     DEVICES 

FOR 

MOTORS 


IGNITION  DEVICES 

FOR 

MOTORS 

WITH     A    CHAPTER 

TREATING  SPECIALLY  OF 

STRUCTURAL   DETAILS,    CHOICE,   AND 
MANAGEMENT  OF  AUTOMOBILES 

By  S.   R.  BOTTONE 

AUTHOR  OF   "AMATEUR  ELECTRICIAN'S   WORKSHOP,"    "TALKING 

MACHINES  &•  RECORDS,"    "ELECTRICAL   ENGINEERING  FOti 

STUDENTS,"    "MODERN  DYNAMOS  &  BATTERIES 

ETC.,  ETC. 

NEW  EDITION,  THOROUGHLY  REVISED  AND  ENLARGED 


JTullp  illustrate* 


'•  "PHILADELPHIA 
DAVID   McKAY,    PUBLISHER 
610,   SOUTH   WASHINGTON  SQUARE 
1911 


Printed  in  England, 


ILLUSTRATIONS. 


PAGE 

Fig.  i.  Section  of  Engine,  front  view          12 

»  2.              5>              55         side  view            13 

„  3A.  Carburetter,  elevation            16 

„  3B-            55           section 17 

„  4.  "  Lantern "  Mixing  Valve      19 

„  5.  Simple  Clutch...         ...         ...         ...         ...         ...  20 

„  6.  De  Dion  Clutch          ,..         ...         ...         ...         ...  20 

„  7.  Darracq  Gear  Box      ...         ...         ...         ...         ...  21 

„  8.  De  Dion          „            22 

,,  9.  Plan  of  Chassis           ...         ...         ...         ...         ...  24 

„  10.  Chassis  as  seen  from  below  ...         ...         ...         ...  25 

„  u.  Differential  Gear        27 

„  12.  Darracq  Steering  Gear         28 

„  13.  Front  View  of  Car      30 

„  14.  Single  Cylinder  Motor          31 

„  15.  Simple  Silencer          32 

„  16.  Universal  Silencer     33 

.,  17.  Parson's  Petroleum  Engine 43 

„  1 8.             „                „              „       showing  Valves        ...  46 

55  19-                         5,                                 „                             ,,                                            ,5                                     .-.  47 

„  20.  Conventional  diagram  of  Armature            59 

„  21.  H  or  Shuttle  Armature          60 

„  22.  Simms'  1900  Motor  with  Magneto 62 

„  23.  The  Bassde  Michel  Magneto           63 

„  24.  The  Dynamo-Coil      67 

„  25.             „                „           ...                                68 

,5  26.             „                 „           69 


267484 


VI  ILL  US TRA  TIONS. 

PAGE 

Fig.  27.   The  Eisemann  Armature      70 

„    28.               „              Magneto       71 

»    29-               „                     „              73 

»    30-  „                      ,,                          .-•                     ...  74 

»    31-               „                     ,,              .-•  75 

»    32.               „                     „              76 

„    33.  „                     »         (wiring)    ...                     ...  77 

»    34-  „                     „                                                ...  78 

»    35-               »                     »             79 

„    36.     Sparking  Plug           80 

„    37.     Simms-Bosch  Arc- Light  Magneto            81 

„    38.     The  Gianoli  Magneto           84 

„    39-             »                    „                 85 

„    40.            „                    „                 86 

„    41.     "  Timing "  the  Spark            97 

„    42.  Major  Torren's  "Primary  Coil"  Sparking  Plug  102 

„    43.  Diagrammatic  Section  of  Secondary  Coil           ...  105 

„    44.     Contact  Breaker       122 

45.  Connection  of  Coil  with  Trembler            127 

46.  Connection  of  Coil  without  Trembler      ...         ...  131 


CHAPTER  I. 

CHOICE  AND  MANAGEMENT  OF  AUTOMOBILES. 

MOTOR  cars,  tri-cars,  and  motor  bicycles 
present  so  much  matter  of  interest,  and 
are  entering  so  largely  into  our  every-day 
life,  that  every  one  should  have  some  knowledge  of 
the  principles  of  their  construction.  This  knowledge, 
even  though  it  be  elementary,  is  absolutely  necessary 
to  the  would-be  purchaser,  otherwise  he  may.be  led 
astray  in  the  choice  of  a  car  by  its  outward  ap- 
pearance, instead  of  directing  his  attention  to 
those  essentials  on  which  the  proper  working  and 
convenience  of  manipulation  depend.  Although 
modifications  and  improvements  are  being  con- 
tinually introduced,  yet  the  main  features  of  the 
propelling  arrangements  adopted  by  nearly  all  auto- 
mobile manufacturers  are  based  on  the  practice  of 
the  leading  makers  in  France,  where,  owing  to  the 
freedom  from  irksome  restrictions  on  the  road,  the 
art  of  constructing  and  working  light,  powerful 
motors,  actuated  by  petrol,  alcohol,  steam,  or  elec- 
tricity, has  reached  a  higher  level  of  perfection  than 
perhaps  in  any  other  country. 

The  first  essential  in  an  automobile  is  the  power  of 
travelling,  and  this  power  it  obtains  from  the  engine. 
The  type  of  motor  now  almost  universally  adopted 
for  the  propulsion  of  automobiles  is  a  modification 


io  ,;.     :,  CHOKE  ,  AND   MANAGEMENT 

of  that  known  as  the  "  internal  combustion  engine." 
In  this  the  power  is  derived  from  the  explosion  of  a 
mixture  of  air  and  petrol  vapour  confined  in  the 
upper  portion  of  a  cylinder,  in  which  travels  a  piston, 
connected  by  a  crank  to  a  fly-wheel,  and  other 
accessories.  Petrol  is  an  extremely  volatile  spirit  (a 
hydro-carbon),  obtained  from  petroleum  by  distilla- 
tion. Being  so  volatile,  it  evaporates  readily,  and 
forms  with  air  a  gaseous  mixture,  which  can  readily 
be  ignited  by  the  electric  spark.  On  being  thus 
fired,  it  explodes,  great  heat  and  consequent  ex- 
pansion occurring  at  the  same  time.  If,  before 
allowing  ignition  to  take  place,  the  gaseous  mixture 
be  compressed,  the  force  of  the  explosion  is  much 
exalted — hence,  greater  power  is  obtainable  from  the 
explosion.  For  this  reason,  in  all  modern  gas  and 
petrol  engines,  great  attention  is  paid  to  obtaining  a 
proper  amount  of  compression  before  firing  the 
mixture.  The  explosion  is  made  to  take  place  by 
means  of  a  "timed"  electric  spark  when  the  com- 
pression of  the  gaseous  mixture  has  reached  a  certain 
predetermined  point. 

We  reproduce  two  outline  illustrations  of  a  typical 
petrol  motor  (Figs.  I  and  2),  in  order  to  enable  the 
reader  to  follow  out  the  principle  on  which  such 
engines  act,  and  this  principle  remains  the  same  in 
all,  although  modifications  are  to  be  found  in  the 
constructional  detail  of  the  engines  turned  out  by  the 
various  makers.  We  may  here  mention  that  the  fly- 
wheel which  is  shown  at  the  back  of  the  lower  portion 
of  Fig.  i,  and  to  the  right  of  Fig.  2,  is  usually  outside 
the  case  of  the  engine  itself;  but  in  some  of  the 
smaller  motors  of  the  cycle  pattern,  it  is  itself 


OF  AUTOMOBILES.  n 

enclosed,  the  spindle  alone  projecting.  Fig.  I  is  a 
front  section,  and  Fig.  2  a  side  view,  of  the  ordinary 
petrol  motor — in  which  I  is  the  cylinder,  2  the 
cylinder  cover,  and  3  the  chamber  containing  the 
crank.  This  chamber  is  fitted  with  two  covers,  4  and 
5,  the  latter  of  which  has  on  it  a  box,  6,  whence 
arises  a  stud,  7,  carrying  a  sleeve.  8,  whereon  is 
formed  the  exhaust-valve  cam.  To  this  sleeve  is 
keyed  the  gear-wheel,  9,  which  is  driven  by  a  pinion, 
10,  fastened  to  the  crank-shaft,  n.  Since  the  number 
of  teeth  on  the  gear-wheel,  9,  is  twice  that  of  those  on 
the  pinion,  10,  it  revolves  at  half  the  speed  of  the 
crank-shaft,  thus  operating  the  exhaust-valve  at  every 
alternate  in-stroke  of  the  piston.  At  12  is  the  piston, 
which  is  furnished  with  three  metal  rings,  13,  which 
enable  it  to  make  a  gas-tight  fit  in  the  cylinder  ; 
and  14  is  the  connecting-rod,  fitted  with  brasses  at 
each  end.  The  valve-box,  15,  is  cast  on  the  side  of 
the  cylinder,  and  communicates  with  the  combustion 
chamber,  16,  by  the  port.  The  valve-box  has  a  water- 
jacket  in  communication  with  the  water-jacket,  29,  30, 
of  the  cylinder,  which  device  prevents  the  valve- 
seatings  becoming  unduly  heated.  At  17  is  an  inlet- 
valve  which  is  automatic  in  its  action,  opening  by  the 
suction  of  the  piston,  against  the  light  spring,  18.  A 
stronger  spring,  20,  controls  the  exhaust-valve,  19, 
which  therefore  resists  the  suction  stroke,  but  is  lifted 
from  its  seat  at  every  second  revolution  of  the  engine 
by  the  cam  on  the  sleeve,  8.  This  cam  raises  the 
roller,  21,  on  the  bell-crank  lever,  22,  pivoted  at  23,  the 
other  end  of  the  bell-crank  lever  having  the  push-rod, 
24,  jointed  to  it.  This  rod  serves  to  lift  up  the  exhaust- 
rod  at  the  right  times.  The  gear-wheel,  9,  is  made 


12  CHOICE  AND  MANAGEMENT 


FIG.  i.— PETROL  MOTOR  (Front  Section). 


OF  AUTOMOBILES. 


FIG.  2. — PETROL  MOTOR  (Side  View,. 


i.4  CHOICE  AND   MANAGEMENT 

of  hard  vulcanised  fibre,  and  on  its  face,  formed  in 
one  piece  with  it,  is  the  disc,  25.  This  serves  to 
"  time  "  the  firing  spark.  On  the  edge  of  the  disc,  25, 
is  the  brass  segment,  26,  which  is  in  metallic  con- 
nection with  the  sleeve,  8.  At  the  extremity  of  the 
stud,  7,  is  an  insulating  plate  (not  shown  in  the 
illustration),  carrying  a  "  brush "  or  spring  which 
presses  on  the  fibre  disc,  26.  By  this  arrangement 
the  electric  circuit  is  completed  once  at  every 
revolution,  between  the  two  extremities  of  the 
primary  of  the  coil,  magneto,  or  other  ignition  device, 
when  the  brush  passes  over  the  brass  segment  on  the 
disc.  This  causes  the  firing-spark  to  be  produced  at 
the  sparking-plug,  which  is  screwed  into  the  valve- 
box  at  27. 

The  mixture  of  petrol  vapour  with  air  produced  in 
the  carburetter,  that  constitutes  the  explosive  mixture, 
is  led  into  the  engine  at  32.  At  28  we  have  the 
aperture  through  which  the  spent,  or  "  exhaust,"  gases 
are  led  away  into  the  silencer.  A  lubricator,  prefer- 
able of  the  "  sight-feed  "  type,  is  either  mounted  on 
the  dashboard  or  screwed  into  the  box  at  31.  In 
order  to  avoid  the  risk  of  any  part  of  the  engine 
" binding"  or  "seizing,"  owing  to  any  neglect  in 
lubricating  the  smaller  bearings,  these  should  be  ar- 
ranged so  as  to  lubricate  themselves  automatically : 
the  studs  carrying  these  are  therefore  drilled  from 
the  inside,  with  holes  reaching  to  these  bearings — 
into  which  holes  sufficient  oil  is  splashed  by  the  crank 
during  its  travel,  or  in  some  cases  a  supply  of  oil  is 
forced  in,  by  means  of  a  small  pump,  situated  near 
ii.  It  is  important  that  the  inlet-valve,  17,  and  the 
exhaust,  19,  should  be  of  ample  area  to  avoid  throt- 


OF  AUTOMOBILES.  15 

tling  the  entering  charge,  or  setting  up  back  pressure 
during  the  exhaust  stroke.  The  water-jacket,  which 
surrounds  the  cylinder  proper,  should  have  no  joints, 
but  be  cast  in  one  piece  with  the  cylinder.  The  en- 
trance for  the  water  is  shown  at  29,  and  its  exit  is  at 
30.  At  these  points,  facings  are  cast  on  the  cylinder, 
to  which  the  flanges  of  the  water  inlet  and  outlet 
pipes  are  attached  by  studs  and  nuts.  In  the  smaller 
cycle-engines  cooling  is  effected  by  the  rush  of  the 
air  between  the  gills  of  the  radiator  when  the  motor 
is  travelling.  These  gills  form  an  external  portion 
of  the  combustion  chamber  and  cylinder.  Some- 
times this  cooling  is  assisted  by  means  of  a  rotary 
fan.  But  in  all  larger  engines  the  cooling  is 
effected  by  water  circulating  in  the  water-jacket  ; 
and  this  circulation  is  frequently  kept  up  by  means 
of  a  small  pump  actuated  by  the  engine  itself. 

The  position  of  the  petrol  tank  and  the  carburetter 
may  be  varied  to  suit  the  build  of  the  car.  We  need 
only  briefly  mention  the  old  form  or  "  surface  "  car- 
buretter, in  which  the  air  entered  into  the  petrol 
through  a  pipe  dipping  into  the  petrol  tank.  The 
air  was  sucked  up  through  the  petrol,  somewhat  in 
the  same  manner  in  which  tobacco  smoke  is  made  to 
bubble  through  the  water  in  a  "  hookah,"  under  the 
action  of  the  suction  of  the  inlet  stroke.  In  so 
doing,  the  air  took  up  a  certain  quantity  of  petrol 
vapour.  But  the  carburetter  which  meets  with  most 
favour  at  present  is  of  the  "spray"  or  pulverising 
type,  in  which  a  certain  given  controllable  quantity 
of  petrol  is  allowed  to  enter  from  the  tank  into  the 
carburetter  by  a  valve  or  faucet — where  it  is  sucked 
up,  broken  into  spray,  mixed  with  air,  and  quickly 


1 6  CHOICE  AND  MANAGEMENT 

vaporised  by  the  suction  of  the  inlet  stroke.  In  this 
"  spray  carburetter,"  one  or  more  tubes,  ending  in 
fine  nozzles,  dip  into  the  petrol,  which  is  sucked  up 
into  the  tube  and  issued  from  the  nozzle  in  the  form 
of  fine  spray,  where  it  meets  with  a  stream  of  air 
also  drawn  in  under  the  influence  of  the  sucking 
action  of  the  inlet  stroke  of  the  engine  itself.  The 


FIG.  3A.— CARBURETTER  (Elevation). 

spray  thus  produced  is  received  in  a  "  mixing  cham- 
ber," into  which  warm  air,  in  suitable  proportions,  is 
simultaneously  being  drawn.  At  Fig.  3  we  give  two 
illustrations  of  the  best  modern  form  of  "  spray 
carburetters." 

The  following  is  a  detailed  description  of  the  sec- 
tional  view  (Fig.  3  B)  : — I.    Air  intake;    2.  Vapour 


OP   AUTOMOBILES. 


FIG  3B.— CARBURETTER  (Section) 


1 8  CHOICE  AND  MANAGEMENT 

outlet  to  engine ;  3.  Casting  of  throttle-valve  or 
sleeve  ;  4.  Sliding  tube  ;  5.  Lever  arm  attached  to 
the  throttle  valve  ;  6.  Sliding  tube  ;  7.  Air  port  ; 
8.  Mixture  outlet  ;  9.  Main  outlet ;  10.  Lever  opera- 
ting tube;  ii.  Outlet  valve;  12.  Lever  to  actuate 
throttle  valve;  13.  Annular  float;  14.  Connections 
of  sliding  tube  to  pin  ;  20.  End  of  screw  ;  21.  Screw 
to  regulate  needle  valve ;  22.  Needle  valve  ;  23. 
Petrol  inlet  ;  24.  Adjusting  spring  ;  25.  Cap  ;  26. 
Water  coupling  ;  27.  Jacket  to  tube  ;  28.  Inflow  tube 
of  water  circulation  ;  29.  Water  coupling  ;  30.  Drain 
cock.  The  petrol  jet  or  sprayer  will  be  seen  in  the 
centre  of  the  illustration  in  the  throttle-valve  casting. 
Working  in  conjunction  with  the  carburetter,  we 
sometimes  have  the  automatic  governor,  which  serves 
to  regulate  the  amount  of  explosive  mixture  supplied 
to  the  combustion  chamber.  It  must  be  noted  that 
there  is  a  definite  proportion  in  which  the  gaseous 
vapour  must  be  mixed  with  air  in  order  to  produce 
the  best  results — this  proportion  being  approximately 
I  part  of  vapour  or  gas  to  18  parts  of  air.  Under 
the  influence  of  the  suction-stroke  of  the  engine,  a 
more  or  less  perfect  vacuum  is  produced  in  the 
carburetter  ;  and,  as  we  have  previously  pointed  out, 
this  causes  both  the  air  and  the  petrol  or  gas  to  rush 
in — the  latter  through  the  spraying  nozzle,  the  former 
through  the  air  inlet.  With  an  increase  of  the  speed 
of  the  engine,  the  amount  of  petrol  sucked  up  and 
sprayed  increases  much  more  rapidly  than  that  of 
the  air — consequently,  the  mixture  becomes  much  too 
rich  in  petrol  to  give  its  best  effect  In  order,  there- 
fore, to  correct  this,  provision  has  to  be  made  to 
admit  more  air  to  dilute  the  richer  mixture  when  the 


OF  AUTOMOBILES.  19 

engine  speed  increases.  This  is  effected  in  different 
manners  by  the  various  makers.  In  the  De  Dion 
type  we  have  the  "lantern"  form  of  mixing  valve 
(Fig.  4).  In  the  latest  pattern  of  Longuemare  car- 
buretters, a  small  flap  valve  covers  the  air  admission  ; 
this  valve  opening  more  and  more  in  proportion  to 
the  suction  of  the  engine,  thus  causing  the  air  supply 
to  be  regulated  practically  automatically. 

We  now  pass  to  consider  briefly  the  methods  usually 


FIG.  4.— "LANTERN"  MIXING  VALVE. 


employed  to  transmit  the  power  thus  generated.  In 
large  stationary  engines  belt  or  rope  drive  is  the  means 
that  finds  most  favour  ;  for  motor  cycles,  the  V  leather 
belt  is  that  almost  universally  adopted,  while  for  motor 
cars  and  other  similar  large  automobiles,  chains,  in 
conjuction  with  friction  clutches,  constitute  the  best 
means  of  transmitting  the  power  from  the  engine  to 
the  wheels.  By  "  friction  clutch"  is  understood  a  disc 
or  drum,  either  of  metal  only,  or  of  metal  faced  with 
leather,  that  by  means  of  a  lever  can  be  caused  to 


20 


CHOICE  AND  MANAGEMENT 


FIG.  c— SIMPLE  CLUTCH. 


FIG.  6. — DE  DION  CLUTCH. 


press  against  the  suitably  coned  surface  of  the  fly- 
wheel, and  thus  partake  of  its  motion.  We  illustrate 
a  simple  form  of  clutch  in  Fig.  5,  in  which  B  is  the 


OF  AUTOMOBILES. 


21 


fly-wheel  on  the  shaft,  A  ;  c  being  the  clutch  proper, 
attached  to  the  transmission  or  clutch  shaft.  Fig.  6  is 
a  sectional  view  of  the  more  elaborate  form  of  clutch 


used  in  the  De  Dion  motor  cars.  The  clutch  can  be 
thrown  into  contact  with  the  fly-wheel,  or  withdrawn 
therefrom,  by  means  of  a  lever.  When  the  clutch  is 


22 


CHOICE  AND  MANAGEMENT 


not  in  contact  with  the  fly-wheel,  the  position  is  said 
to  be  neutral^  or  the  engine  is  "out  of  gear,"  so  that, 
although  the  engine  may  be  working,  the  car  is  not 
propelled.  The  motion  thus  imparted  to  the  clutch 
is  carried  by  the  clutch  shaft  to  a  "  gear  box,"  wherein 
are  contained  two  shafts,  on  one  of  which  (called 
the  primary)  are  fixed  three  cog-wheels  of  somewhat 
different  diameters,  with  more  or  fewer  teeth.  On 


Fio.  8  -DE  DION  GEAR  Box. 

the  other  (the  secondary)  which  is  square,  are  ar- 
ranged other  cog-wheels  carried  by  a  sleeve.  This 
sleeve  can  be  slid  along  its  shaft  by  means  of  a  lever, 
so  that  one  or  other  of  its  gear-wheels  can  be  caused 
to  mesh  at  will  with  any  given  one  of  the  wheels  on 
the  other  shaft,  and  thus  slacken,  increast,  or  even 
reverse  the  rotation.  We  give  at  Figs.  7  and  8  illus- 
trations of  good  forms  of  gear  boxes  ;  the  former 


OF  AUTOMOBILES.  23 

being  the  type  favoured  by  Darracq  &  Co.,  while  the 
latter  is  the  one  adopted  by  De  Dion  Bouton  &  Co. 
In  this  illustration  the  arrangement  which  allows 
one  wheel  to  travel  faster  or  slower  than  the  other,  so 
as  to  enable  the  car  to  turn  corners,  is  also  shown  in 
part. 

The  power  having  been  fchus  carried  as  far  as  the 
change-speed  gear  box,  is  now  transmitted  to  the 
driving-wheels — either  directly,  by  means  of  suitable 
pinions  from  the  secondary  shaft  to  the  rear  wheels 
through  the  differential,  or  else  by  means  of 
sprocket  wheel  and  chains  to  the  rear  wheels.  We 
show,  at  Fig.  9,  the  position  of  these  relative  parts. 
In  this  illustration  37  represents  the  engine,  behind 
which  is  seen  the  clutch  ;  a  shaft  proceeding  from 
which  carries  the  power  to  the  change-gear  box. 
It  must  be  noted  that,  in  order  to  take  up  any 
strain,  this  shaft  is  jointed  to  the  clutch,  and  again 
to  the  shafc  of  the  gear  box,  by  means  of  a 
form  of  Hook's  joint,  known  as  a  "  cardan."  This 
joint  consists  practically  in  two  forks  set  at  right 
angles  to  one  another,  with  crossed  pins  between 
them,  so  that  if  the  driving  wheels  were  to  fall 
or  rise  owing  to  any  inequality  in  the  road,  no 
strain  would  thereby  be  put  on  this  shaft.  In  this 
illustration,  directly  behind  the  change-speed  gear 
box,  is  seen  the  differential,  which,  as  we  have  already 
explained,  enables  one  of  the  wheels  to  turn  inde- 
pendently of  the  other. 

It  must  be  remembered  that,  in  the  modern  types 
of  motor  cars,  the  engine,  with  its  radiator,  is  placed 
in  front,  near  the  steering  wheels,  while  the  driven 
wheels  are  invariably  at  the  back  of  the  car.  This 


CHOICE  AND   MANAGEMENT 


OF  AUTOMOBILES. 


I     3 


1118  § 


26  CHOICE  AND   MANAGEMENT 

may  be  clearly  seen  in  Fig.  10,  which  shows  the 
position  of  all  the  parts  as  seen  from  below.  Before 
going  farther  we  may  explain  the  manner  in  which 
the  differential  works.  It  consists,  as  shown  at  Fig. 
1 1,  of  three  or  more  conical  gear  wheels,  carried  on  a 
portion  of  the  driving  shaft.  These  small  conical 
gear  wheels,  shown  in  the  centre  of  the  illustration, 
mesh  into  the  teeth  of  two  crown  wheels — that  in  the 
illustration  appear  standing  a  little  apart  from  them 
to  the  right  and  to  the  left,  but  which,  when  in  action, 
mesh  firmly  into  the  conical  gear  wheels.  These  two 
crown  wheels  themselves  are  fixed  to  the  inner  ends 
of  the  two  halves  of  the  axle,  which  is  cut  at  this 
portion  and  supported  by  sleeves.  A  moment's  con- 
sideration will  show  that  when  the  gear  is  in  mesh, 
although  the  axle  is  in  two  pieces,  it  acts  as  though 
it  were  one  solid  shaft,  and  the  rate  of  motion  of  both 
wheels  is  the  same  ;  but  if  by  any  means  one  road 
wheel  be  held  back  (by  greater  friction  on  the  road, 
or  otherwise),  the  mere  fact  of  its  retardation  will, 
by  the  action  of  the  cone-crowned  wheel,  cause  the 
other  road  wheel  to  travel  faster. 

We  now  pass  on  to  consider  the  method  adopted 
for  steering.  The  front  axle  has  two  jointed  ends 
on  which  the  steering  wheels  are  free  to  rotate  ;  and 
these  two  ends  are  connected  together  by  means  of  a 
cranked  bar,  so  that  any  motion  given  to  this  bar  is 
imparted  to  both  wheels.  The  steering  is  effected 
on  the  wheel  and  inclined  pillar  principle,  and  con- 
sists of  a  pillar  or  shaft  mounted  on,  and  passing 
through,  a  hollow  standard  attached  to  the  floor  of  the 
car,  at  a  considerable  angle  of  inclination.  The 
upper  end  terminates  in  a  large  wheel  within  easy 


OF  AUTOMOBILES.  27 

reach  of  the  driver,  while  the  lower  extremity  is 
connected  to  a  simple  form  of  worm  gear  with  a  rather 
quick  thread,  which  engages  in  a  toothed  quadrant ; 


^fcs?   » 


this  latter  being  pivoted  and  carrying  an  arm.  This 
arm  is  connected  up  to  one  of  the  steering  axles  by 
means  of  a  jointed  rod.  The  two  axles  being,  as 


28 


CHOICE  AND    MANAGEMENT 


aforesaid,  connected  together,  it  is  evident  that,  when 
the  steering  wheel  is  turned,  the  screw  or  worm  will 
cause  the  quadrant  arm  to  push  the  connecting-rod 


FIG.  12. — DARRACQ  STEERING  GEAR. 


backwards  or  forwards,  thus  conveying  the  motion 
to  the  two  wheels.  Our  Fig.  12  will  give  a  clear  idea 
of  the  construccion  of  the  steering  arrangements. 


OF  AUTOMOBILES.  29 

It  will  be  noticed  that  this  system  is  quite  irrever- 
sible, so  that  road  shocks  cannot  affect  the  position 
of  the  wheels.  Consequently,  the  steering  is  per- 
fectly under  control  of  the  driver,  with  a  minimum  of 
exertion  on  his  part.  The  mode  in  which  the  movable 
ends  of  the  axle  are  strongly  connected  to  the  rigid 
central  portion  is  well  shown  at  the  two  sides  of  Fig.  1 3. 

The  position  of  the  water  tank,  of  the  petrol  tank, 
and  of  the  carburetter,  is  largely  a  matter  of  conve- 
nience ;  in  any  case,  easy  access  should  be  obtainable 
to  the  mechanism  by  opening  in  front,  or  otherwise. 
Tne  radiator,  of  which  we  give  an  illustration  at  Fig. 
13,  is  usually  placed  in  front,  and  is  kept  cool,  not 
only  by  the  circulation  of  water  (either  natural  or 
artificially  driven  by  a  small  pump),  but  also  by 
the  rush  of  air  through  the  honeycombed  surface 
of  the  radiator,  sometimes  assisted  by  a  draught 
created  by  a  rotary  fan.  Besides  these  essential 
portions,  every  motor  car  is  furnished  with  a  removable 
cranked  handle,  by  means  of  which  the  engine  can 
be  started  by  hand  without  driving  the  road  wheels, 
until  it  has  drawn  the  exploded  mixture  from  the 
carburetter  into  the  cylinder,  and  fired  a  charge  or 
two  (the  road  wheels  having  been  previously  thrown 
out  of  gear  with  the  engine  by  moving  the  clutch 
handle  into  the  neutral  position)  ;  after  which  it  can 
be  allowed  to  do  its  work  automatically,  and  the  road 
wheels  thrown  into  gear  when  required. 

In  the  foregoing  description  we  have  only  men- 
tioned a  single-cylinder  engine  ;  the  reader  must, 
however,  be  prepared  to  meet  with  many  cars  that 
are  furnished  with  two,  four,  or  even  six  cylinders. 
In  these  cases  there  is  no  particular  difference  in  the 


30  CHOICE  AND  MANAGEMENT 

construction  of  each  cylinder  (which  are  generally 
cast  in  one  case),  except  only  that  the  cranks,  which 


o 
2  «. 

§£ 

>H        O 

w  — . 
z, 

o 


are  connected  to  the  fly-wheel,  are  usually  placed  at 
such  an  angle  that  they  receive  the  impulses  of  the 


OF  AUTOMOBILES.  31 

explosions,  not  simultaneously,  but  at  different  por- 
tions of  their  stroke.  This  is  effected  by  setting  the 
cranks  at  an  angle  of  180°  from  each  other.  By 
this  means  a  very  good  balance  is  obtained  ;  and  the 
explosions,  or  impulses,  follow  one  another  in  quick 


FIG.  14. — 8  H.P.  SINGLE-CYLINDER  MOTOR. 

succession.     In   the  case  wherein  two  pistons  move 
in  the  same  direction  simultaneously,  it  is  not  so  easy 
to  obtain  a  good  balance.      At  Fig.   14  the  readei 
will  find  an  illustration  of  a  single-cylinder  engine  of 
the  Darracq  type. 

Although  not  essential  to  the  efficient  working  of 


32 


CHOICE   AND  MANAGEMENT 


a  petrol  or  gas  engine,  a  device  intended  to  minimise 
the  noise  made  by  the  out-rush  of  the  exploded 
mixture,  and,  therefore  known  as  a  "  silencer,"  is  now 
universally  adopted.  The  scope  of  the  silencer  is  to 
lower  the  pressure  of  the  escaping  spent  gases  before 
they  come  into  contact  with  the  outer  atmosphere. 
For  this  purpose  the  "exhaust  "  gases  are  led  from 
the  engine  into  a  chamber  or  box,  generally  of  steel 
or  aluminium,  in  which  the  initial  pressure  at  which 
these  were  ejected,  is  reduced  by  meeting  with  re- 
sistance. In  the  simplest  form,  Fig.  15,  the  silencer 


A 


QSSS 
Jil 


FIG.  ic. — SIMPLE  SILENCMJ. 


consists  of  two  tubes — the  inner  and  smaller  one  of 
which  fits  on  the  exhaust  (see  No.  28  of  Figs,  i  and 
2)  of  engine,  and  is  itself  surrounded  by  a  second  and 
larger  tube,  closed  at  both  ends.  Both  these  tubes 
are  perforated  round  their  sides  with  numerous  small 
holes,  and  it  is  in  passing  through  them  that,  the 
exploded  gases  meet  with  resistance,  and  conse- 
quently become  reduced  in  pressure.  The  greater 
the  pressure  at  which  the  exhaust  gases  issue,  the 
more  noise  will  be  made  by  their  impact  with  the 
air.  Hence,  in  all  good  silencers,  every  precaution  is 


OF  AUTOMOBILES. 


33 


taken  to  reduce  the  pressure  quickly,  and,  at  the  same 
time,  not  to  produce  "  back  pressure,"  which  would 
greatly  militate  against  the  proper  working  of  the 
engine.  Few  people  are  aware  of  the  enormous 
influence  the  silencer  may  exert  in  this  direction. 
In  one  of  the  latest  forms  of  silencers,  the  spent 
gases,  after  leaving  the  exhaust,  enter  by  a  perforated 
tube  into  an  hour-glass-shaped  receiver,  from  the 
further  end  of  which  they  pass  through  numerous 
perforations  into  an  outer  cylindrical  casing,  whence 
they  finally  issue  at  the  same  end,  but  on  the  outside 


FIG.  16. — UNIVERSAL  SILENCER. 


of  the  tube  by  which  they  originally  entered.     Fig. 
16  is  a  section  of  this,  the  "  Universal  "  Silencer. 

The  only  point  that  now  needs  notice  is  that  con- 
nected with  the  brake,  by  means  of  which  pressure 
can  be  brought  to  bear  either  on  the  wheels  them- 
selves, or  on  the  differential,  so  as  to  assist  in  checking 
the  motion  when  it  is  required  to  stop  the  car. 
The  brake  gear  varies  with  different  makers.  In 
some  cases  it  takes  the  form  of  a  band  which  is 
tightened  round  a  drum  forming  part  of  the  axle, 
either  in  continuation  with  the  change-speed  gear,  or 


34  CHOICE  AND  MANAGEMENT 

with  the  differential.  This  latter  plan  is  not  par- 
ticularly recommended,  as  it  may  strain  the  differen- 
tial itself.  Or  it  is  effected  by  means  of  what  is  known 
as  the  expanding  clutch,  in  which  a  pair  of  metal  seg- 
ments of  a  circle,  united  together  at  one  extremity 
by  a  pin,  so  that  they  can  open  out  somewhat  like 
the  legs  of  a  pair  of  compasses,  are  caused  to  expand 
and  press  against  the  inside  of  a  drum,  under  the 
action  of  an  oblong  piece  of  metal  pressing  near  the 
joint,  by  the  influence  of  the  brake  handle  or  pedal. 

A  word  or  two  as  to  the  series  of  operations  to  be 
executed  in  starting  the  car  may  not  be  out  of  place 
here.  The  petrol  and  water  tanks  must  first  be  filled,' 
the  former  with  good  petroleum  spirit  having  a  sp.  gr. 
of  O'68  at  60°  Fahr.,  the  latter  with  clean,  preferably 
soft,  water.  The  ignition  apparatus,  be  it  coil  and 
accumulator,  or  magneto  and  its  attachments,  should 
be  then  looked  to,  especially  as  regards  good  and 
clean  contacts.  When  an  accumulator  is  used,  its 
electrical  condition  must  be  ascertained,  and  the 
E.  M.  F.  of  each  cell  carefully  measured  by  voltmeter. 
It  should  show  2  volts  per  single  cell,  or  4  volts  for 
the  usual  double-cell  form,  and  must  not  be  allowed 
to  fall  below  1-9  in  the  former,  or  3-8  volts  in  the 
latter  case,  without  re-charging. 

When  filling  the  tank  with  petrol,  a  funnel  with  a 
fine  gauze  filter  should  be  used,  to  prevent  any 
particles  of  dirt  from  passing  in  with  the  petrol.  In 
the  absence  of  fine  gauze,  a  piece  of  very  fine  linen 
may  be  employed.  The  radiator  is  now  to  be  filled 
with  water  through  the  top  cap.  Before  starting  up, 
it  should  be  seen  that  the  change-speed  lever  is  in 
the  neutral  notch,  that  the  hand-brake  is  "  on  "  :  and 


OF  AUTOMOBILES.  35 

that  the  petrol  tap  is  open.  The  main  switch  should 
then  be  turned  "on,"  and  the  "timing"  lever  moved 
to  its  fully-retarded  position,  so  that  the  ignition  will 
occur  immediately  after  the  cranks  have  passed  the 
inner  dead  centre,  and  no  risk  will  be  run  from  back- 
firing. Afterwards,  the  starting-handle  (crank)  is 
taken  in  the  right  hand  and  pressed  inwards  towards 
the  motor,  turning  the  handle  from  bottom  to  top, 
clockwise.  This  motion  is  continued  steadily,  but 
not  necessarily  with  any  great  expenditure  of  energy, 
until  nearing  the  top,  and,  at  this  instant,  the  move- 
ment of  the  crank  is  accelerated,  in  order  -to  cause  the 
crank-shaft  to  pass  quickly  over  the  upper  dead 
centre.  The  motor  should  then  start.  This  ac- 
celeration is  usually  followed  by  the  automatic  with- 
drawal of  the  crank-handle  as  the  crank-shaft  runs 
ahead  of  the  engaging. 

Should  the  motor  not  start,  lifting  slightly  for  a 
moment  the  float-needle  so  as  to  "  flood "  the  car- 
buretter, and,  if  necessary,  putting  a  few  drops  of 
petrol  in  each  cylinder  through  the  compression  taps, 
will  remedy  the  defect.  As  soon  as  the  motor  turns, 
it  is  well  to  make  sure  that  the  water  circulation  is 
working  properly,  and  that  the  lubricator  is  correctly 
adjusted  to  give  the  required  feed  of  oil.  The  driver 
then  takes  his  seat,  holding  the  steering-wheel  in  his 
left  hand  and  depressing  the  clutch-pedal  with  his 
left  foot.  He  then  brings  back  the  brake-lever 
(which  had  been  applied),  and  changes  over  the 
change-speed  lever  from  the  neutral  notch  to  the 
first-speed  notch  ;  if  a  slight  resistance  be  felt,  he 
should  not  attempt  to  force  the  lever,  but  should 
allow  the  clutch-pedal  to  rise  slightly  for  a  moment, 


36  CHOICE  AND  MANAGEMENT 

fully  depressing  it  again,  and  the  lever  can  then  be 
slowly  moved  into  the  notch,  easily  and  noiselessly. 
Then  he  gradually  lets  in  the  clutch. 

To  pass  from  one  speed  (gear)  to  a  higher  one  he 
will  always  begin  by  de-clutching,  then  move  the 
lever  up  one  notch  and  let  the  clutch  in  gently,  as 
before  recommended.  To  revert  to  a  lower  "  gear," 
he  should  never  attempt  to  effect  this  until  the  car's 
speed  has  fallen  almost  to  the  one  desired.  In 
ascending  a  steep  hill,  a  lower  gear  should  be  brought 
into  play  as  soon  as  the  car  shows  any  decided 
tendency  to  slow  down.  Under  ordinary  circum- 
stances the  speed  of  the  car  is  controlled  solely  by 
regulating  that  of  the  engine,  or,  when  slowing  down 
for  traffic,  by  simply  de-clutching.  In  other  cases 
when  a  quick  stop  or  a  rapid  slackening  of  speed 
is  necessary,  besides  de-clutching,  the  brakes  should 
be  used.  The  clutches  should  be  always  let  in  gently. 
To  pass  from  the  forward  motion  to  the  reverse  the 
car  should  always  be  brought  to  a  complete  standstill 
and  the  change  speed  lever  be  brought  back  to  the 
neutral  notch  before  any  attempt  is  made  to  introduce 
the  reversing  gear.  For  a  sharp  stop,  both  brakes 
should  be  applied.  On  a  long  descent,  or  in  cases  in 
which  the  brakes  have  to  be  used  for  some  time,  they 
should  be  used  alternately  to  avoid  heating.  In 
preference,  the  hand-brake  should  be  used,  which,  as 
it  acts  directly  on  the  back  wheel,  does  not  strain  the 
differential. 

At  the  conclusion  of  a  run  the  driver  should  make 
an  invariable  practice  of  seeing  that  the  hand-brake 
is  applied  before  he  leaves  the  seat,  and  that  the 
change-speed  lever  is  quite  in  its  neutral  notch.  He 


OF  AUTOMOBILES.  37 

should  then  stop  the  motor  by  turning  off  the  switch, 
and  should  close  the  petrol  feed-tap.  It  is  always 
advisable  at  the  end  of  a  day's  run  to  clean  the  inside 
of  the  cylinder.  For  this  purpose  the  compression 
taps  should  be  opened,  and  in  them  a  spoonful  of 
paraffin  should  be  poured.  The  motor  is  then  gently 
turned  until  no  more  vapour  from  the  paraffin  leaves 
the  taps.  By  this  means  any  sediment  liable  to  clog 
the  piston  rings  is  dissolved  away. 

If  the  engine  does  not  start  after  the  crank-handle 
has  been  turned  as  above  described,  and  fails  to  do  so 
after  two  or  three  attempts,  it  is  probable  that  the 
proportions  of  air  and  petrol  vapour  in  the  explosive 
mixture  are  not  correct,  or  that  the  ignition  apparatus 
requires  attention.  The  explosive  mixture  can  be 
adjusted  by  altering  the  position  of  the  air  and 
vapour,  levers  until  the  motor  fires  regularly.  The 
alteration  in  the  supply  of  air  and  of  vapour  must  be 
done  carefully  and  gradually,  as  a  very  little  makes  a 
vast  difference  in  the  result.  It  is  quite  worth  while 
to  try  the  effect  of  making  alterations  in  the  quality 
and  quantity  (richness  in  petrol  vapour)  of  the 
mixture,  as  the  experience  gained  by  such  a  pro- 
cedure is  far  more  valuable  than  any  amount  of 
theorizing.  Of  course,  in  all  motors  fitted  with  auto- 
matic regulation  of  air  and  petrol  in  the  carburetter, 
the  above  precautions  will  hardly  ever  be  required. 
The  car  should  always  be  started  slowly,  remem- 
bering that  the  speed  can  be  slackened  by  closing  the 
throttle  valve,  and  that  the  ignition  should  be 
advanced  for  high  speeds  or  retarded  whenever  the 
engine  is  running  more  slowly,  from  whatever  cause. 

The   following    excellent    hints,    based    on  those 


38  CHOICE  AND   MANAGEMENT 

drawn  up  by  J.  W.  Packard,  embody  the  chief  points 
to  be  attended  to  and  avoided  in  motor-car  driving  ; 
"Do  not  forget  to  turn  on  the  petrol  and  spark  before 
attempting  to  start  Don't  forget  to  turn  oil  on,  and 
to  close  any  half-compression  device  that  may  be 
fitted  to  the  engine  after  starting.  Don't  try  to 
run  the  carriage  without  oil  in  any  of  the  oil-cups. 
Don't  try  to  run  without  petrol  in  tanks.  Don't 
leave  your  car  with  water  in  the  tank  or  jackets 
in  frosty  weather.  Don't  jerk  in  your  clutch  ;  bring 
it  up  gradually.  Never  let  the  engine  knock.  Don't 
start  down  a  hill  at  a  rapid  rate  and  then  jam  on  the 
brakes.  Don't  try  to  turn  corners  rapidly,  par- 
ticularly if  the  brakes  are  on.  Don't  forget  to  turn 
off  all  lubricators  when  shutting  down.  Don't  tighten 
clutches  so  that  they  drag  or  bite.  Don't  neglect  to 
turn  off  petrol  at  night.  Don't  take  anything  to 
pieces  unless  it  is  absolutely  necessary,  and,  even 
then,  without  noticing  how  it  is  put  together.  Don't 
neglect  to  keep  all  contact  points  clean.  Don't  allow 
any  bellhanger  or  cycle  repair  man  to  add  'im- 
provements '  to  your  car.  Don't  use  cheap  or  poor 
lubricating  oil.  Don't  let  your  engine  '  race  '  at  any 
time,  or  run  at  an  excessive  speed  when  using  low- 
speed  gear.  Don't  leave  your  car  unattended  with 
engine  running.  Don't  leave  your  licence  at  home. 
Don't  expect  that  all  you  have  to  do  is  to  pull  the 
lever ;  learn  to  understand  thoroughly  the  mechanism 
and  adjustment  of  your  machine." 

Lubrication  is  a  very  essential  point  in  the  work- 
ing of  a  motor-car.  We  have  already  pointed  out 
how  the  smaller  bearings  are  automatically  lubri- 
cated by  the  "splashing"  of  the  crank  in  its  travel — 


OF  AUTOMOBILES.  39 

oil  being  supplied  by  means  of  holes  drilled  for  this 
purpose  into  the  studs  connected  with  these.  The 
oil  is  injected  into  the  crank  case  at  intervals,  and 
is  carried  in  a  container  fixed  on  the  dash-board  of 
the  car.  A  pump  is  combined  with  this,  and,  by  this 
means,  a  charge  of  oil  can  be  injected  into  the  crank 
case  when  required.  In  many  cars  an  automatic 
device  supplies  the  oil  from  the  tank,  or  container, 
into  a  number  of  tubes  leading  to  the  engine,  bear- 
ings, pumps,  etc.,  the  oil  being  forced  up  a  tube  in 
the  centre  of  the  container  by  means  of  pressure 
from  the  exhaust  box.  The  oil  used  for  these 
smaller  parts  must  be  of  a  thinner  nature  than  that 
employed  for  the  gear  boxes  and  heavier  gearing, 
and  should  flow  freely. 

The  nature  of  the  oil  to  be  used  will  vary  with  the 
parts  to  be  lubricated  ;  as  a  general  rule,  we  may  say 
that  the  thickest  mineral  (hydro-carbon)  oil  that  will 
How  freely  will  be  the  most  advantageous.  The  ten- 
dency with  motor  drivers  at  the  present  day  is  to  use 
a  thin  oil.  For  water-cooled  motors,  an  oil  of  medium 
viscosity,  which  will  stand  a  fire  test  of  470°  Fahr. 
without  charring,  will  be  found  generally  useful.  For 
gear  boxes,  a  heavy  black  hydro-carbon  oil,  standing 
a  fire  test  of  400°  Fahr.  will  be  found  most  suitable. 
By  "black"  we  do  not  mean  dirty  oil,  but  simply 
the  natural  dark  colour  of  the  oil.  Many  drivers 
use  semi-solid  lubricants  in  the  gear  boxes  ;  to  this 
there  is  no  objection,  provided  the  lubricant  can  find 
its  way  to-  the  parts  at  which  lubrication  is  needed, 
as  a  semi-solid  lubricant  has  the  advantage  of  pre- 
venting the  entrance  of  dust,  dirt,  and  grit,  to  the 
bearings.  It  must  be  remembered  that  the  gear 


40  CHOICE  AND  MANAGEMENT 

boxes  must  be  real  "oil  baths,"  so  that  the  gear 
wheels  themselves  dip  half  way  into  the  oil.  Many 
employ,  for  this  latter  purpose,  lubricants  containing 
finely-divided  graphite  or  plumbago,  and  this,  except 
for  the  difficulty  of  application,  is  an  ideal  lubricant. 
As  it  is,  in  the  case  of  a  bearing  or  piston  which  has 
got  slightly  injured  through  want  of  lubrication,  it  is 
perhaps  the  only  thing  that  will  bring  the  surfaces 
back  again  into  good  condition. 

Most  careful  attention  must  be  given  to  timely 
lubrication  of  the  engine,  and  the  container  should 
be  replenished  at  intervals  of  not  more  than  an  hour, 
or  an  hour  and  a  half  of  actual  running  time.  On 
the  other  hand,  the  lubrication,  especially  with  lighter 
oils,  must  not  be  overdone,  though,  with  well-con- 
structed engines,  precautions  are  taken  to  prevent 
any  surplus  oil  finding  its  way  into  the  combustion 
chamber. 

In  the  choice  of  a  car,  the  following  points  require 
careful  notice.  There  should  be  as  few  moving  parts 
as  is  consistent  with  obtaining  the  movements  de- 
sired. All  machinery  should  be  easily  accessible. 
Water  tank,  water  circulation,  or  other  means  of 
cooling  should  be  ample  ;  lubrication  also  readily 
effected.  A  very  important  part  is  that  all  portions 
should  be  interchangeable,  and  be  capable  of  being 
supplied  by  the  maker  of  the  car.  Lock-nuts  should 
be  of  the  helicoidal  type.  The  machine  should  be 
strongly  built  so  that  repairs  may  limit  themselves 
to  the  replacement  of  worn  or  damaged  parts. 
Wherever  there  are  wearing  parts,  provision  must  be 
made  that  the  wear  may  be  readily  taken  up  by  the 
users.  With  regard  to  the  engines  proper,  the  best 


OF  AUTOMOBILES.  41 

result  is  obtained  by  fitting  these  vertically — horizon- 
tally placed  engines  being  almost  entirely  discarded. 
An  engine  requiring  to  run  at  an  excessive  speed  to 
give  its  listed  power,  should  also  be  avoided  ;  most 
modern  motor-car  engines  give  their  normal  output 
at  an  average  speed  of  1,800  R.P.M  Ribs  in  cylinder 
covers  not  only  strengthen  the  same,  but  help  to 
dis^pate  the  heat  by  radiation.  The  silencer  should 
be  chosen  to  work  as  noiselessly  as  possible,  consistent 
with  not  producing  any  appreciable  back  pressure. 

A  governor  which  automatically  reduces  the  speed 
of  the  engine  when  the  car  is  stopped,  is  a  great 
convenience.  If  too  much  complication  be  not  in- 
troduced in  effecting  the  result,  that  type  of  lubrica- 
tion which  automatically  cuts  off  the  supply  of  oil 
when  the  engine  comes  to  a  standstill,  is  desirable. 
The  amount  of  petrol  used  will  naturally  vary  not 
only  with  the  power  of  the  engine,  but  also  with  the 
amount  of  work  put  upon  it.  We  have  purposely 
omitted  any  detailed  description  of  the  timing  appa- 
ratus used  in  connection  with  the  electrical  firing 
device  employed  for  the  purpose  of  igniting  the 
gaseous  mixture  supplied  to  the  combustion  chamber 
by  the  carburetter.  This,  as  we  have  already  noticed, 
consists  in  a  fibre  disc  actuated  by  the  half-speed 
shaft  (see  Fig.  I,  26);  and  we  shall  reserve  fuller 
description  until  we  treat  of  the  different  forms  of 
electric  ignition  which  constitute  the  subject  of  our 
next  chapter. 

We  can  hardly  conclude  this  chapter  without 
some  notice  of  those  combustion  engines  which 
are  specially  adapted  either  for  stationary  work 
or  for  the  driving  of  launches.  In  these  it  is 


42  CHOICE  AND  MANAGEMENT 

convenient  to  be  able  to  use  a  cheaper  hydro- 
carbon than  petrol,  and,  in  the  case  of  launches, 
very  much  safer.  There  has,  therefore,  naturally 
arisen  an  urgent  demand  for  an  engine  using  paraffin 
or  other  safe  heavy  oil,  in  as  satisfactory  a  manner  as 
petrol  ;  and  this  demand  has  been  rendered  greater 
because  petrol  is  costly  when  used  in  the  quantities 
required  in  a  motor  boat ;  wheras  paraffin  is  cheap,  and 
moreover,  easily  procurable.  Its  drawback,  however, 
lies  in  the  fact  that  an  engine  cannot  be  started  on  it 
when  all  is  cold,  and  it  usually  becomes  a  question  of 
heating  a  vaporiser  by  a  blow-lamp,  or  running 
on  petrol  until  the  exhaust  gases  have  heated  the 
vaporiser.  The  former  method  means  that  starting 
cannot  be  effected  immediately,  as  with  petrol  ;  and 
this,  under  certain  circumstances,  may,  in  a  boat, 
lead  to  serious  consequences.  Many  engineers  have 
been  engaged  on  solving  this  problem,  and  we  have 
selected  as  an  illustration  of  the  manner  in  which 
this  difficulty  can  be  overcome  the  Parsons'  engine, 
not  because  it  is  the  only  one  of  its  kind,  but  because 
it  is  typical  of  all  that  is  best  in  the  fulfilment  of 
the  requirements  of  the  case.  It  will  be  borne  in 
mind  that  such  engines  are  not  required  to  run  at  high 
speeds,  but  are  intended  for  long  runs  at  full  power, 
and,  therefore,  the  Parsons'  engine  is  not  to  be  classed 
with  the  light  motor-car  engines  using  petrol  only, 
and  running,  for  the  most  of  the  time,  throttled  down. 
In  the  first  place,  no  external  vaporiser  is  used, 
nor  is  any  lamp  used  for  starting,  so  that  there  is  no 
possibility  of  its  blowing  out,  or  ejecting  burning  oil, 
or  requiring  cleaning.  To  start  such  an  engine,  of 
which  we  give  an  illustration,  in  section,  at  Fig.  17,  a 


OF  AUTOMOBILES. 


43 


FIG.  17.— THE  PARSONS'  ENGINE  (SECTION). 


44  CHOICE  AND  MANAGEMENT 

little  petrol  is  used  in  the  carburetter,  not  necessarily 
more  than  the  float-chamber  full  ;  and  this  is  arranged 
for,  either  by  fitting  a  small  filler  to  the  carburetter, 
or  by  connecting  a  small  tank  to  the  two-way  cock. 
The  former  plan  does  away  entirely  with  the  petrol 
tank  and  accompanying  pipes,  and  there  is  then  only 
paraffin  connected  with  the  carburetter  ;  the  latter 
plan  affords  the  advange  that  the  engine  can  be  run 
on  either  fuel,  as  desired.  If  a  filler  is  used  for  start- 
ing, then  a  portable  air-tight  can  is  provided,  holding 
enough  petrol  for,  perhaps,  a  dozen  starts,  and  filled 
as  required.  Alcohol  fuel,  or  any  mixture  of  fuel,  may 
be  used  instead  of  paraffin,  and  in  the  same  way. 
In  all  cases,  the  fuel  is  used  through  the  same  carbu- 
retter, which  is  of  the  ordinary  petrol  type,  and  not 
what  is  known  as  the  paraffin  carburetter,  requiring 
heat  for  the  vaporisation  of  the  fuel.  After  starting 
on  petrol,  the  paraffin,  or  other  fuel,  is  turned  on,  and 
the  engine  continues  to  run  with  no  more  smoke 
or  smell  than  with  petrol.  Sometimes  it  is  necessary 
to  alter  slightly  the  feed  adjustment  to  the  jet  of  the 
carburetter  according  to  the  fuel  used,  by  means  of 
the  adjustable  needle  valve ,  but,  if  set  for  one  fuel, 
it  need  not  be  altered  for  starting  on  petrol. 

Referring  to  the  section  of  the  engine  here  shown, 
it  will  be  seen  that  the  valves  are  combined,  and  that 
the  exhaust  valve  is  seated  upon  the  hollow  tubular 
inlet  valve.  The  exhaust,  in  passing  through  the 
latter,  heats  it  up  and  emerges  through  ports  at  the 
bottom  of  the  valve,  and  away  out  at  the  exhaust 
connection.  The  paraffin  is  vaporised  ,  but  only 
the  moment  before  it  enters  the  cylinder.  When 
using  paraffin  there  is  no  vaporisation  in  the  car- 


OF  AUTOMOBILES.  45 

buretter,  and  no  additional  heat  required  for  it ;  and, 
therefore,  there  can  be  no  subsequent  recondensation 
in  pipes  between  the  carburetter  and  the  inlet  valve, 
nor  can  any  liquid  paraffin  reach  the  combustion 
chamber.  The  vaporisation  is  perfect,  and  the  amount 
of  heat  such  that  no  prejudicial  effect  is  noticeable 
even  if  the  engine  continues  to  run  on  petrol.  In  the 
latter  case,  warm  air  from  near  the  exhaust  pipe  is 
supplied  to  the  carburetter  ;  but  with  paraffin  this 
warming  is  not  necessary.  Both  valves  are  mechani- 
cally operated  by  separate  cams  ;  but  while  the 
exhaust  valve  has  full  lift,  the  inlet  valve,  owing  to 
its  large  area,  has  about  half  the  lift  as  the  exhaust, 
yet  the  opening  is  the  same,  owing  to  its  large 
diameter.  No  extra  work  is  put  upon  the  cams  and 
rollers,  as  the  large  valve  lifts  on  the  suction-stroke 
only.  One  spring,  cotter,  and  washer,  closes  both 
valves  ;  and,  on  the  exhaust  stroke,  the  inner  valve 
only  lifts,  whilst  on  the  inlet  stroke  both  lift 
together — the  exhaust  remaining  seated  upon  the 
inlet.  All  gear-wheels  are  enclosed,  and  there  is 
only  one  cam  shaft.  The  crank  chamber  can  be 
taken  apart  without  disturbing  the  crank  shaft,  etc.  ; 
and  in  all  sizes,  except  the  "single  cylinder,"  the  sup- 
porting arms  are  in  one  with  the  lower  half  of  the 
crank  chamber,  which  thus  forms  a  bed-plate  and 
avoids  anything  getting  out  of  line  if  the  engine  is 
separated  for  adjustment.  In  all  models  of  the  Par- 
sons' engine,  a  universal  joint  is  provided  for  connec- 
tion to  a  propeller  shaft,  thus  allowing  a  vertical 
engine  with  a  raking  shaft.  We  may  also  mention 
that,  up  to  the  28  or  32  h.p.  engines,  the  crank  shaft 
is  carried  by  the  upper  half  of  the  crank  chamber,  so 


46 


CHOICE  AND  MANAGEMENT 


that  this,  along  with  the  cylinders,  piston,  crank  shaft, 
etc.,  all  come  away  together,  thus  avoiding  drawing 
pistons  out  of  cylinders. 


FIG.  1 8. — THE  PARSONS'  ENGINE. 
(POSITION  OF  VALVES  ON  THE  INLET  STROKE.) 

Ample  water  space,  easily  cleaned  out,  is  provided 
round  cylinder  and  valves — the  water  being  supplied 
by  a  pump,  as  usual.  The  lubrication  is  automatic 


OF  AUTOMOBILES. 


47 


in  all  parts.  The  exhaust  branch  pipe  in  the  multi- 
cylinder  engines  is  arranged  to  allow  for  its  expansion 
when  hot,  so  as  not  to  force  the  cylinders  out  of  line, 


FIG.  19. — THE  PARSONS'  ENGINE. 
(POSITION  OF  VALVES  ox  THE  EXHAUST  STROKE.) 

and  all  connections  are  so  designed  that  any  one 
cylinder  may  be  removed  easily  without  disturbing 
the  others. 


48       MANAGEMENT  OF  AUTOMOBILES. 

Ignition  is  usually  arranged  by  battery  and  coil ; 
but,  if  desired,  a  "  Bottone "  enclosed  dynamo  or 
magneto  can  be  fitted,  driven  by  the  engine,  and  so 
connected  that  the  engine  starts  on  the  battery,  runs 
on  the  dynamo,  and,  at  the  same  time,  keeps  the 
accumulator  charged — the  dynamo  furnishing  low 
tension  current  to  the  coil  in  the  same  way  as  the 
battery.  This  is  a  simple  and  reliable  duplicate 
ignition,  which  has  stood  the  test  of  time,  and  has 
none  of  the  drawbacks  of  the  usual  low  or  high  ten- 
sion ignition  ;  whilst,  should  the  dynamo  break  down 
(a  very  unlikely  thing),  there  is  always  the  battery  to 
fall  back  upon.  With  regard  to  the  oil  consumption, 
from  trials  recently  made,  it  was  found  that  about 
four- fifths  of  a  pint  of  paraffin  was  used  for  each 
brake-horse-power  hour  ;  and,  in  the  reliability  tests, 
in  which  a  Parsons'  boat  gained  the  highest  mark 
— only  fifteen  gallons  of  paraffin  were  consumed 
in  as  many  hours  when  running  at  about  ten  knots, 
which  gives  about  a  farthing's-worth  of  paraffin  for  a 
nautical  mile. 


CHAPTER    II. 
VARIOUS  METHODS  OF  IGNITION. 

EVER  since  the  advent  of  the  gas-engine,  and 
of  its  congener,  the  fi  oil-engine,"  much 
ingenuity  has  been  displayed  in  the  con- 
struction of  suitable  contrivances  for  igniting  the 
explosive  mixture.  It  will  be  evident,  on  the 
slightest  consideration,  that  the  conditions  to  be 
fulfilled  will  necessarily  vary  with  the  varying  cir- 
cumstances in  which  the  engine  is  to  be  employed, 
and  that  an  igniter  which  would  be  eminently 
suitable  for  a  stationary  gas-engine  might  be  quite 
inapplicable  to  a  portable  petrol  motor  forming  part 
of  a  motor-car,  or  of  a  motor-bicycle.  As  so  much 
interest  has  of  late  been  evinced  in  this  subject,  we 
make  no  apology  for  presenting  the  following  epitome 
of  the  more  important  devices  in  use  for  this  purpose, 
with  a  few  remarks  as  to  their  fitness  or  unsuitability 
for  certain  particular  requirements. 

In  the  very  earliest  commercially  successful  gas- 
engine — that  of  M.  Lenoir  (1860) — the  means  adopted 
for  firing  the  explosive  mixture  was  an  electric  spark. 
As  in  this  engine  no  attempt  was  made  to  secure 
compression  of  the  gaseous  mixture,  no  particular 
care  was  taken  to  time  the  spark.  As  the  piston 
advanced  it  drew  in  an  explosive  mixture  of  gas  and 
air,  and  about  mid-stroke  this  was  ignited  by  an 
electric  spark. 


50       VARIOUS  METHODS   OF  IGNITION. 

In  the  Otto  and  Langen  engine  (1867),  in  which 
also  there  was  no  compression,  the  ignition  was 
effected  by  a  small  gas  flame,  to  which  the  gaseous 
mixture  gained  access  at  the  desired  moment  through 
the  action  of  a  special  slide-valve,  which  opened  and 
closed  a  port-hole  facing  the  gas  flame.  In  the  Otto 
engine  of  1876  compression  was  adopted,  and  the 
compressed  mixture  was  fired  just  when  the  forward 
stroke  was  about  to  begin,  by  means  of  a  slide-valve 
alternately  uncovering  and  covering  a  hole  facing  a 
small  gas  flame.  In  the  "  Priestman "  petroleum 
engine,  electric  ignition,  in  the  shape  of  sparks 
generated  by  an  induction  coil,  was  the  means  first 
adopted  ;  the  slide-valve  being  the  same  as  in  the 
Otto. 

In  more  recent  forms  of  stationary  oil-engines  the 
ignition  is  effected  by  a  flame  produced  by  a  blow- 
through  oil  lamp,  of  the  "yEtna"  or  "Primus"  type, 
but  this  lamp  itself  requires  frequent  attention  to 
keep  up  the  supply  of  vaporised  oil  on  which  its  own 
flame  depends.  For  all  stationary  work  no  form 
of  ignition  is  perhaps  so  satisfactory  as  that  adopted 
by  Crossley  Bros.,  in  which  a  tube,  either  of  porcelain 
or  of  a  suitable  metal,  is  kept  nearly  white-hot  by  a 
Bunsen  flame  playing  in  its  interior. 

Neither  tube  nor  direct  flame  ignition  lends  itself 
readily  to  small  petrol  motors,  such  as  are  usually 
adopted  in  motor-cars,  tri-cars,  and  bicycles ;  and  for 
these  electric  ignition  presents  many  advantages. 
The  means  employed  for  igniting  by  electricity  are 
various : — Firstly,  maintaining  a  thin  platinum  wire 
(placed  close  to  the  slide-valve)  in  a  state  of  incan- 
descence by  the  current  from  a  battery.  Secondly, 


VARIOUS  METHODS   OF  IGNITION.      5* 

producing,  by  the  aid  of  a  coil  and  battery,  a  con- 
tinuous stream  of  sparks  before  the  slide-valve. 
Thirdly,  the  production  with  the  coil  and  battery  of 
sparks  between  the  platinum  points  of  an  igniter, 
which  is  inserted  in  the  explosion  chamber  of  the 
engine,  the  time  at  which  these  sparks  take  place 
being  controlled  by  a  cam,  or  other  device  that  makes 
(or  breaks)  the  circuit  at  the  required  instant. 
Fourthly,  the  production  of  sparks  directly  from  a 
magneto-machine,  or  from  a  dynamo  driven  by  the 
motor  itself.  Fifthly,  producing  sparks  from  a  com- 
posite machine  called  a  "  dynamo-coil,'1  in  which  the 
field-magnet  and  its  winding  form  at  the  same  time 
the  core  and  primary  of  the  sparking  coil,  which 
therefore  admits  of  accurate  timing  of  the  spark  by 
interrupting  the  circuit  in  the  primary.  Of  these  the 
first  may  be  dismissed  from  further  consideration, 
since  it  is  very  difficult  to  maintain  a  platinum  wire 
at  the  point  of  incandescence  by  the  battery  current 
without  either  fusing  it,  if  the  current  exceeds  the 
normal,  or  allowing  it  to  become  too  cool  if  the 
current  falls  below  that  point.  Besides  this  defect 
the  platinum  wire  is  very  apt  to  become  encrusted 
with  unburnt  carbon  derived  from  the  gas.  The 
fourth  method  is  open  to  the  objection  that  efficient 
sparks  are  produced  by  the  magneto  (or  dynamo) 
only  when  the  speed  at  which  it  is  driven  reaches  a 
certain  point;  and,  moreover,  that  when  that  speed  is 
increased,  there  is  considerable  risk  of  breaking  down 
the  insulation  of  the  generator.  These  objections 
have  not  much  weight  when  the  engine  is  stationary, 
running  at  a  practically  constant  speed  ;  but  they 
become  serious  in  cases  of  motor-cars,  or  any  other 


52       VARIOUS   METHODS   OF  IGNITION. 

vehicles  in  which  the  speed  is  liable  to  sudden  varia- 
tions. We  are,  therefore,  driven  to  the  conclusion 
that  coil  ignition  in  some  form  or  other  is  the  best  for 
general  purposes.  It  may  be  pointed  out  here  that 
even  in  the  case  of  stationary  engines  electric  ignition 
is  superior  to  any  form  of  flame  or  tube,  as  it  econo- 
mises gas  or  vapour. 

Whatever  form  of  coil  be  adopted  (with  the  sole 
exception  of  the  dynamo  or  magneto  and  coil  and  its 
modifications)  a  battery  must  be  employed  in  con- 
junction with  it,  to  supply  the  current  necessary  to 
cause  it  to  produce  sparks.  Now,  it  is  just  at  the 
battery  that  all  the  troubles  begin.  In  stationary 
engines  it  is  a  nuisance  to  have  to  replace  dry  cells} 
or  to  dismount  and  remount  primary  cells  of  any 
kind.  The  former  quickly  fail  to  give  sufficient 
current,  and  must  be  replaced  ;  the  latter  more 
gradually,  but  just  as  surely,  lose  power,  and  must  be 
renovated.  The  only  battery  that  can  be  depended 
upon  to  give  a  sufficiently  equable  current  for  any 
length  of  time  is  an  accumulator  of  fairly  large 
ampere-hour  capacity.  This  is  really  the  best — we 
might  say  the  only  satisfactory — source  of  current 
which  can  be  used  for  working  the  coil.  But  the 
accumulator  must  be  recharged.  This  is  not  a 
serious  matter  in  the  case  of  stationary  engines, 
where  access  can  be  had  to  a  charging  station,  or 
where  a  portion  of  the  power  of  the  engine  can  be 
diverted  from  the  general  work  to  drive  a  dynamo 
from  which  a  spare  accumulator  can  be  charged. 
But  when  we  come  to  deal  with  accumulators  to  be 
fitted  into  petrol-engined  launches,  motor-cars,  or 
motor-bicycles,  in  which  so  much  depends  on  the 


VARIOUS  METHODS  OF  IGNITION.      53 

condition  of  the  accumulators,  and  when  it  is  fre- 
quently impossible  to  have  recourse  to  a  charging 
station,  some  means  of  maintaining  the  accumulator 
charged  to  a  working  point  becomes  a  matter  of  the 
highest  importance. 

We  can  now  pass  to  the  consideration  of  the 
requirements  in  a  dynamo  suitable  for  stationary  gas 
or  petroleum  engines.  Circumstances  only  can 
decide  whether  it  will  be  more  convenient  to  allow  a 
portion  of  the  spare  power  of  the  engine  to  be  em- 
ployed continuously  for  the  purpose  of  keeping  the 
accumulators  charged,  or  whether  a  certain  time  in 
each  day  shall  be  set  aside  to  attain  this  end.  In  the 
former  case  the  dynamo  must  be  fitted  with  some 
automatic  device  (called  a  "cut-in  and  cut-out") 
which  shall  break  the  circuit  between  the  dynamo 
and  the  accumulator  whenever  the  dynamo  gives  less 
than  the  required  charging  voltage,  and  shall  com- 
plete the  circuit  when  the  voltage  reaches  the 
necessary  point.  The  automatic  cut-in  and  cut-out  is 
an  absolute  necessity  in  all  cases  in  which  the  engine 
is  subjected  to  variations  in  speed,  due  to  different 
loads  being  put  on  it.  In  the  case  of  a  certain  time 
each  day  being  set  aside  solely  for  charging,  the  em- 
ployment of  the  cut-out,  though  convenient,  is  not 
imperative,  since  the  dynamo  attendant,  by  keeping 
his  eye  on  the  voltmeter,  can  immediately  switch  out 
the  dynamo  if  he  finds  the  voltage  falls  below  the 
necessary  2-5  volt  per  cell. 

It  is  hardly  necessary  to  remark  that  whatever 
type  of  dynamo  be  employed  it  must  be  shunt 
wound,  or,  if  compound,  the  shunt  coils  alone  must  be 
employed.  Series  wound  machines  and  alternators 


54      VARIOUS  METHODS  OF  IGNITION. 

are  of  no  use  for  this  purpose.  The  particular  type  of 
machine  is  of  no  great  moment ;  ring  and  drum  arma- 
tures are  the  best,  but  the  outward  form,  all  other 
things  being  equal,  is  of  some  importance.  In  large 
establishments  in  which  the  dynamo  can  be  kept 
away  from  the  general  workshops,  any  good  dynamo, 
whether  open  or  enclosed,  is  admissible,  and  in  fact 
the  open  type  presents  some  advantage  in  allowing 
easy  access  to  the  brushes  for  regulation.  But  in  all 
cases  in  which  dirt  or  dust  is  present  in  the  dynamo- 
room  the  machine  should  be  of  the  enclosed  type. 
We  do  not  mean  by  this  that  the  dynamo  should 
simply  be  enclosed  by  a  covering,  whether  of  wood  or 
of  metal ;  but  that  its  construction  should  be  such 
that  the  entirety  of  its  working  parts  (with  the  excep- 
tion of  shaft  and  driving  pulley)  should  be  enclosed 
in  iron,  this  iron  forming  an  active  portion  of  its 
field -magnet  system.  The  first  real  iron -clad 
dynamo  was  devised  by  Mr.  Tighe  in  1882.  In 
this  a  single  wound  pole  arose  from  the  centre  of 
an  iron  cylinder,  the  top  of  the  cylinder  being  dome- 
shaped  and  forming  the  other  pole  of  the  dynamo, 
the  armature  playing  between  the  central  pole-piece 
and  the  dome.  A  very  similar  pattern,  excepting 
that  the  cylinder  terminated  in  a  circular  cap,  was 
designed  by  Mordey  for  the  Brush  Company.  This 
form  has  been  largely  adopted  by  more  recent  makers 
as  being  at  once  efficient,  compact,  and  having  its 
working  parts  fully  protected  by  the  missive  outer 
iron  cylinder  or  case. 

The  exterior  form  of  the  enclosed  dynamo  is  evi- 
dently not  of  so  much  moment  as  its  adaptability  to 
the  varying  speeds  to  which  it  may  be  subjected.  In 


VARIOUS  METHODS   OP   IGNITION.      55 

the  earlier  types  of  enclosed  dynamos,  dating,  as  we 
have  seen,  from  about  1882,  and  applied  principally  to 
keeping  up  the  charge  in  accumulators  for  stationary 
engines,  neither  the  question  of  weight  nor  the  capa- 
bility of  self-adaptation  to  great  and  sudden  variations 
in  speed  were  of  paramount  importance.  But,  with 
the  advent  of  the  automobile,  it  became  imperative  that 
the  dynamo  should  be  at  once  light,  compact,  efficient, 
and  capable  of  being  driven  at  greatly  different 
rates,  without  either  injuring  the  accumulators,  which 
it  is  destined  to  charge,  or  risking  the  breakdown  of 
its  own  insulation.  It  is  difficult  to  unite  in  one 
machine  all  these  requirements.  If  the  dynamo  be 
very  small,  and  contain  but  little  iron,  it  must  be 
driven  at  a  high  speed,  and  must  be  wound  with 
fine  wire,  and  this  fine  wire  presents  resistance  to  the 
current,  which  results  in  heating.  To  be  efficient,  the 
dynamo  must  have  a  certain  amount  of  iron  in  it, 
duly  proportioned  to  the  wire  on  the  armature  and 
field-magnet  system.  This  means  that  all  the  metal 
parts  of  the  enclosed  dynamo  should,  as  far  as  pos- 
sible, be  of  iron,  and  that  this  iron  should  form  an 
active  portion  of  the  field  magnet  and  armature. 
This,  of  course,  does  not  apply  to  the  armature  con- 
ductors, nor  to  the  F.M.  coils  which  are,  in  all  modern 
machines,  of  copper. 

By  carefully  proportioning  the  machine  it  is  pos- 
sible to  construct  an  enclosed  dynamo,  weighing 
about  6  Ibs.  to  8  Ibs.,  which  shall  be  well  able  to  charge 
the  four-volt  accumulators  usually  employed  in  motor 
cars,  etc.  If  the  machine  take  the  form  of  an  upright 
cylinder,  or  even  a  square  box,  with,  of  course,  the 
contained  upright  field-magnet  core  and  armature,  it 


56      VARIOUS  METHODS   OF  IGNITION. 

is  possible  to  construct  it  so  that  no  electrically 
useless  metal  is  used  except  that  for  the  bearings,  the 
brushes,  and  the  lubricator.  But  this  leaves  untouched 
the  question  of  speed  variation.  As  far  as  injury  to  the 
accumulator  is  concerned,  this  difficulty  can  be  got 
over  in  several  ways — such  as,  for  instance,  a  hand- 
governed  resistance,  more  and  more  of  which  can  be 
switched  in  when  and  as  the  speed  increases.  Or  an 
automatic  cut-in  and  cut-out  can  be  adopted,  which 
shall  complete  the  circuit  when  the  speed  attains  a 
certain  point,  and  break  it  again  if  it  exceed  a 
given  range,  to  remake  it  when  the  speed  falls  to 
within  the  "  safe  charging  limit."  But  an  automatic 
cut-out  is  rather  delicate  in  its  action,  and  the  jolt- 
ing and  trembling  of  the  motor  car  is  not  conducive 
to  its  satisfactory  behaviour.  Neither  of  the  above- 
mentioned  devices,  nor  indeed  anything  external 
to  the  dynamo,  can  prevent  injury  to  this  latter  it 
the  speed  be  greatly  in  excess  of  the  normal.  But  it 
is  possible  to  control  the  output  of  the  dynamo  by 
altering. the  strength  of  its  magnetic  field,  and  this 
can  be  done  automatically  by  cutting  out  more  and 
more  of  the  field-magnet  coils  as  the  speed  increases, 
or,  what  amounts  to  the  same  thing,  automatically 
inserting  a  dead  resistance  in  the  field-magnet  circuit 
when  this  occurs. 

Having  pointed  out  the  requirements  for  electric 
ignition,  we  will  proceed  to  describe  briefly  the  more 
successful  appliances  that  have  been  employed  for  the 
purpose.  The  first  device  (apart  from  the  coil)  which 
was  used  was  a  modification  of  Breguet's  "torpedo 
exploder."  In  this,  a  soft-iron  armature  was  hinged  in 
front  of  the  poles  of  a- powerful  compound  permanent 


VARIOUS  METHODS   OF  IGNITION.      57 

magnet,  the  two  limbs  of  which  were  coiled  with  fine 
wire.  On  striking  a  lever  attached  to  the  armature 
this  latter  was  suddenly  removed  from  its  proximity 
to  the  poles  of  the  said  magnet ;  returning  after  the 
stroke  by  the  action  of  a  spring  in  connection  with 
the  lever.  This  sudden  motion  of  the  armature,  by 
setting  free  the  magnet's  lines  of  force,  induced  a 
current  of  high  E.M.F.  in  the  coils  surrounding  the 
magnet's  limbs,  which  current  was  led  by  suitable 
wire  to  the  slide-valve  opening,  or  to  the  ignition  plug 
of  the  engine,  where  it  produced  a  spark.  The  lever 
was  actuated  by  a  cam  on  the  half-speed  shaft  of 
the  engine  itself. 

In  order  to  facilitate  a  clear  conception  of  the 
manner  in  which  the  electric  current  is  set  up  by 
means  of  magnets,  be  these  permanent,  as  in  the 
case  of  "  magnetos,"  or  temporary,  as  in  dynamos, 
it  will  not  be  out  of  place  here  to  refresh  the  reader's 
memory  by  stating  the  fact,  that  around  the  poles 
of  every  magnet  (be  it  permanent  or  temporarily 
energized  by  the  circulation  of  an  electric  current) 
there  exists  a  space,  permeated  by  the  magnetic 
force,  exerted  by  the  magnet ;  this  space  is  called 
"the  magnetic  field,"  and  the  directions  in  which 
this  force  is  manifested  are  known  as  "the  lines  of 
force." 

It  must  be  distinctly  understood  that  these  terms 
are  merely  convenient  methods  of  expressing  our 
views,  and  that  there  are  no  more  tangible  lines  of 
force  emanating  from  a  magnet  than  there  are 
"rays"  of  light  emanating  from  a  candle.  Still,  a 
very  good  idea  may  be  obtained  of  the  direction  and 
distribution  of  the  magnetic  force  round  a  magnet's 


58      VARIOUS  METHODS  OF  IGNITION. 

poles  by  laying  a  sheet  of  white  paper  over  the  poles 
of  a  horseshoe  magnet,  and  lightly  sifting  on  it  some 
fine  iron  filings,  which,  on  gently  tapping  the  paper, 
will  be  seen  to  arrange  themselves  in  positions 
indicating  the  distribution  of  the  magnetic  force,  but 
in  one  plane  only. 

Now  it  is  found  that  if  any  conductor  be  moved 
between  the  poles  of  a  magnet  so  as  to  "cut"  these 
imaginary  lines  of  force,  a  current  of  electricity  is  set 
up  in  the  conductor,  which  current  will  vary  in 
strength  in  accordance  with  the  number  of  lines  cut 
in  a  given  time.  In  like  manner,  if  a  conductor, 
previously  shielded  from  the  action  of  a  magnet's 
poles  (by  means  of  an  iron  screen  or  otherwise),  be 
suddenly  exposed  to  their  action  by  the  removal  of 
the  screen,  a  current  is  momentarily  set  up  ;  and 
again,  another  current  (in  the  opposite  direction)  is 
elicited  if  the  shielding  screen  be  as  suddenly 
replaced.  In  order  to  "  cut "  the  lines  of  force,  it  is 
evident  that  either  the  conductor  or  the  screen  must 
be  moved ;  and  as  rotary  motion  is  the  most  convenient 
in  practice,  it  is  usual  to  arrange  the  conductor  (or 
conductors)  lengthwise  round  the  periphery  of  a 
cylinder  of  soft  iron,  mounted  on  a  spindle,  and 
capable  of  being  rotated.  Such  an  arrangement  is 
known  as  an  "armature."  A  typical  view  of  an 
armature,  with  a  single  turn  of  wire  (conductor) 
passed  lengthwise  over  and  under  it,  is  shown  at 
Fig.  20.  This  is  illustrated  as  lying  between  the 
extensions  N  S  (known  as  "  pole-pieces  "),  of  a  horse- 
shoe magnet.  The  shaded  parts  indicate  the  magnetic 
lines  of  force  ;  the  arrow  shows  the  direction  of 
rotation  imparted  to  the  armature  ;  while  the  letters  P 


VARIOUS  METHODS   OF  IGNITION.       59 

(positive),  N  (negative),  denote  the  electrical  conditon 
of  the  conductor,  A  B,  in  different  portions  of  its  travel. 
From  this  it  will  be  seen  that,  on  starting  from  the 
top  of  the  figure,  and  moving  counter-clockwise 
towards  the  north  pole  of  the  magnet,  the  conductor, 
A,  at  first  practically  cuts  no  lines  of  force,  but  simply 
glides  between  them  ;  but  as  it  continues  its  travel,  it 
cuts  an  increasing  number  of  these  lines,  until  it  has 
travelled  through  90°  of  arc,  when  the  maximum 


FIG.  20. 


number  of  lines  is  reached.  This  is  also  the  point 
where  the  electro- motive  force,  and  therefore  the 
current  set  up,  is  at  its  highest.  Continuing  the 
motion,  the  number  of  lines  cut  and  the  current 
resulting  therefrom  decreases,  until  on  arriving  at 
1 80°  no  lines  are  cut,  and  therefore  no  current  is 
evolved. 

The  observant  reader  will  notice  that  the  electrical 
condition    of   the   extremity,   A,   of    the    conductor 


60       VARIOUS  METHODS  OF  IGNITION. 

besides  rising  and  falling,  while  it  passes  from  o°  to 
1 80°,  changes  from  positive  to  negative  as  it  com- 
mences its  upward  journey  from  180°  to  360°,  owing 
to  its  cutting  the  lines  of  force  in  the  opposite  direction. 
This  means,  that  if  we  collect  the  current  evolved  at 
the  extremity,  A,  of  the  conductor,  during  one  entire 
revolution,  we  shall  find  it  change  direction  at  each 
semi-revolution.  In  practice,  for  ignition  purposes, 
it  is  immaterial  whether  the  current  delivered  by  the 
armature  be  unidirection  or  alternating,  so  that 
usually  the  extremity,  A,  of  the  wire,  or  conductor,  is 
connected  up  to  an  insulated  metal  ring  on  the  spindle, 
while  the  opposite  extremity  is  fastened  bodily  to 


FIG.  21. — H  OR  SHUTTLE  ARMATURE. 

the  iron  cylinder  of  the  armature  itself,  through 
which  it  can  complete  the  circuit  through  the  frame 
of  the  engine,  cycle,  or  car.  Also,  as  the  electrical 
effects  are  exalted  in  proportion  to  the  number  of 
conductors  cutting  the  lines  of  force,  armatures  are 
not  fitted  with  a  single  conductor,  but  are  channeled 
out  longitudinally ;  and  in  the  channel  is  wound 
several  hundred  turns  of  wire — the  starting  and 
terminating  extremities  of  which  are  brought  out 
and  connected  as  described  above.  A  complete 
armature,  wound  with  wire  longitudinally  in  the 


VARIOUS  METHODS  OF    IGNITION.     61 

channel — usually  bound  to  prevent  the  wire  rising 
by  centrifugal  tendency— is  shown  at  Fig.  21,  where 
the  brass  caps  or  "heads,"  to  which  the  spindle  is 
affixed,  and  which  bear  the  the  insulated  ring  con- 
nected to  one  extremity  of  the  armature  wire,  are 
also  depicted. 

The  current  produced  is  picked  up,  on  the  one 
side,  by  the  frame  of  the  engine,  and,  on  the  other, 
by  a  spring  or  "  brush "  which  presses  against  the 
insulated  ring.  If,  instead  of  using  a  continuous 
ring  to  collect  the  current,  a  number  of  separate  seg- 
ments, each  insulated  from  its  neighbour,  be  arranged 
in  an  annular  form  on  the  spindle,  and  the  opposite 
segments  be  connected  to  the  opposite  extremities, 
A  and  B,  of  the  conductor,  or  conductors  wound  on 
the  armature,  it  is  possible  to  collect,  by  means  of 
two  insulated  "  brushes  "  pressing  against  the  opposite 
sides  of  this  segmental  collector,  or  "  commutator,"  a 
current  that  will,  flow  continuously  in  one  direction, 
and  be  "  alternating."  But  in  magneto  machines  for 
ignition  purposes,  "  rectified "  currents  are  rarely 
employed.  On  the  other  hand,  they  are  largely 
employed  in  lighting,  plating,  and  accumulator  charg- 
ing, for  which  dynamos,  fitted  with  commutators, 
are  alone  admissible. 

To  the  above  brief  outline  of  the  mode  in  which  a 
magneto  or  a  dynamo  acts,  we  need  only  add  one 
fact — of  a  knowledge  of  which  makers  of  magnetos 
avail  themselves  in  the  construction  and  application 
of  these  machines  for  ignition  purposes — and  this  is, 
that  if  the  current  flowing  through  the  armature  be 
suddenly  arrested,  a  much  heavier  discharge  takes 
place  than  is  due  to  the  lines  of  force  cut,  owing  to  a 


62       VARIOUS  METHODS   OF  IGNITION. 

kind  of  electrical  momentum  set  up  in -the  wire 
coiled  in  the  armature,  which  momentum,  in  expend- 
ing itself,  sets  up  a  momentary  current  in  the  opposite 


FIG.  22.— SIMMS  MFG.  Co.'s  1900  sf-H.p.  MOTOR,  FITTED  WITH 
SIMMS- BOSCH  MAGNETO. 


direction,  exceeding  the  original  current  in  intensity, 
in  proportion  to  the  number  of  turns  of  wire  there 
are  wound  on  the  armature. 


VARIOUS  METHODS   OF  IGNITION,       63 

A  more  modern  application  of  the  magneto 
•machine  to  the  purpose  of  ignition  was  that  known 
as  the  "  Simms-Bosch."  In  this  we  had  three  per- 
manent horseshoe  magnets,  bestriding  the  pole- 
pieces,  in  which  was  bored  out  a  cylindrical  tnnnel  to 
take  the  armature.  The  armature  itself  was  a  fixture, 
wound  with  wire  suitable  to  produce  the  required 


FIG.  23. — THE  BASSEE  MICHEL  MAGNETO. 


spark,  which  was  obtained,  not  by  causing  the  arma- 
ture to  rotate  or  to  oscillate  so  as  to  cut  lines  of 
force,  but  by  imparting  a  reciprocating  movement  to 
a  soft-iron  envelope,  which  lay  between  the  armature 
and  the  magnets,  and  which,  by  virtue  of  this  move- 
ment, uncovered  the  wound  portion  of  the  armature, 
giving  rise  to  a  momentary  electric  current,  which 
evidenced  itself  in  the  form  of  a  spark  at  the  ignition- 


64       VARIOUS  METHODS   OF  IGNITION. 

plug.  As  in  the  Breguet  magneto,  the  motion  was 
imparted  by  a  cam  and  lever  on  the  engine.  The 
Simms-Bosch  magneto  admitted  of  very  accurate 
timing,  and  marked  a  distinct  advance  upon  the  older 
form  in  which  the  armature  moved. 

Fig.  22  represents  the  Simms-Bosch  magneto  igniter 
in  position  on  the  Simms  motor.  The  weight  of  these 
appliances  varies  with  the  purpose  and  speed  for 
which  they  are  intended.  Thus,  for  stationary 
engines,  running  at  not  less  than  60  R.P.M.,  the  weight 
is  28  Ibs. ;  for  automobiles,  to  run  at  not  less  than  300 
R.P.M.,  20  Ibs. ;  for  very  light  work,  cycles,  etc.,  at  a 
speed  of  not  less  than  300  R.P.M.,  the  weight  is  7j  Ibs. 

Magneto  igniters  of  this  type,  in  which  the  current 
(owing  to  the  wire  wound  on  the  armature  being  of 
coarse  gauge)  is  rather  large  in  volume,  but  of  com- 
paratively speaking  low  E.M.F.,  are  usually  spoken 
of  as  "  low-tension  magnetos." 

As  another  example  of  this  form  of  magneto,  we 
give,  at  Fig.  23,  an  illustration  of  the  Bassee  Michel, 
which  is  extensively  used  in  the  De  Dion  cars.  The 
armature,  A,  revolves  at  the  speed  of  the  crank  shaft, 
and  is  driven  direct  by  means  of  the  cardan-jointed 
spindle  and  sleeve,  D.  It  runs  on  ball  bearings  shown 
at  each  end  of  the  spindle,  which  are  lubricated  at  L. 
It  has  five  compound  magnets,  M  M  M  M  M,  a  current 
terminal  at  T,  a  condenser  at  C,  and  an  insulated 
plate,  which  presses  against  a  spring  thrust-pin,  S. 
One  end  of  the  armature  is  insulated,  as  shown  at 
•I.  At  each  half  turn  of  the  armature,  the  current, 
alternately  +  and  — ,  passes  through  the  contact 
breaker  at  the  moment  when  the  current  has  reached 
its  maximum. 


VARIOUS  METHODS  OF  IGNITION.      65 

Closely  allied  to  the  low-tension  magneto  is  the 
very  neat  and  efficient  igniter  brought  out  in  1899 
by  the  Elbridge  Electrical  Manufacturing  Co.,  U.S.A. 
Two  sizes  were  put  on  the  market  ;  the  larger, 
marked  "  S,"  being  a  circular  carcass,  two-pole 
drum  armature  dynamo,  series  wound  ;  size  10  ins. 
high  and  about  10  ins.  from  end  to  end  of  shaft. 
The  weight  is  47  Ibs.  Owing  to  the  special  construc- 
tion and  winding  of  this  machine,  no  "sparking"  or 
"induction"  coil  is  needed,  a  bright  spark  being 
always  obtained  at  the  breaking  of  the  circuit.  This 
dynamo  will  not  lose  its  magnetism  when  short- 
circuited,  and  will  always  increase  its  output  at  the 
moment  when  the  spark  is  obtained.  The  bearings 
are  extra  long,  lined  with  Babbitt  metal,  and  the  lubri- 
cation is  effected  by  "  wick "  oilers,  the  reservoirs 
holding  enough  oil  for  a  week's  run.  The  commutator 
is  constructed  of  tempered  copper,  and  is  very  wide. 
The  brushes  are  of  carbon  of  ample  carrying  capacity, 
and  no  harm  is  done  if  the  dynamo  be  accidentally 
run  backwards.  The  normal  speed  of  this  machine 
is  1,400  R.P.M.,  and  as  all  the  working  parts  are 
included  in  the  frame  of  the  machine,  they  are  well 
protected  from  external  injury. 

A  smaller  size,  "  R,"  is  intended  specially  for  small 
launches,  automobiles,  and  where  the  larger  machine 
would  be  too  heavy.  The  general  principles  of  con- 
struction are  the  same ;  but  the  dynamo  itself  is  of 
the  "  enclosed  "  type,  so  as  to  protect  the  working 
parts  from  dust  and  dirt.  The  weight  is  only  14  Ibs., 
which  is  less  than  that  of  an  ordinary  coil  and  accu- 
mulators ;  the  height  is  6\  ins.,  and  the  extreme 
length  9!  ins.,  while  the  normal  speed  for  driving  to 


66      VARIOUS  METHODS  OF  IGNITION. 

give  good  sparks  is  1,600  R.P.M.  Special  attention 
is  given  to  all  bearings,  so  that  the  machine  can  be 
run  continuously  for  a  long  period  without  showing 
appreciable  wear.  The  brushes  are  of  carbon  and 
copper  combined,  thus  insuring  good  conductivity 
and  sparklessness.  The  bearings  are  made  of 
Holmes's  "  fibre-graphite  "  composition,  and  require 
no  oil  whatever.  Owing  to  the  nature  of  the  circuit, 
these  Elbridge  sparking  dynamos  require  the  em- 
ployment of  a  " wiping"  or  dotting  contact  at  the 
point  of  spark  production.  They  are  not  adapted 
for  use  with  the  ordinary  sparking  plug,  in  which 
there  is  a  gap  between  two  platinum  points. 

In  the  "  dynamo-coil  "  protected  by  the  writer  in 
1899,  the  problem  of  obtaining  a  steady  and  certain 
flow  of  "  hot "  sparks,  as  from  an  induction  coil, 
without  the  annoyance,  weight,  and  uncertainty  of 
batteries  or  accumulators,  was  first  successfully 
grappled  with. 

The  dynamo-coil,  as  its  name  implies,  is  a  hybrid 
between  a  dynamo  and  an  induction  coil.  Let  the 
reader  imagine  an  ordinary  series-wound  dynamo  of 
such  size  and  shape  as  to  fit  easily  into  the  space 
generally  allotted  to  the  sparking-coil  in  a  motor  car. 
It  is  convenient,  though  by  no  means  indispensable, 
that  there  should  be  only  one  field-magnet  core,  and 
this  built  of  the  softest  iron  wire  possible.  Around 
this  are  wound  the  series  coils  of  the  dynamo  proper. 
So  far,  there  is  practically  no  difference  between  this 
and  an  ordinary  series-wound  dynamo.  Over  the 
series  coils,  but  quite  independent  of  them,  and  well 
insulated,  are  wound  several  thousand  turns  of  fine 
wire,  precisely  similar  to  the  secondary  of  an  induction 


VARIOUS  METHODS   OF  IGNITION.      67 

coil,  the  two  extremities  of  which  are  connected  to 
terminals  (or  other  electrodes)  that  serve  to  convey 
the  induced  current  to  any  point  at  which  it  is  desired 
to  produce  the  spark.  Fig.  24,  which  is  a  partially 
sectional  view  of  one  of  the  older  types  of  the 
"  dynamo-coil,"  gives  an  idea  of  the  general  dis- 
position of  the  parts,  but  does  not  indicate  the  proper 
connection  to  firing  plug,  the  devices  by  which  the 
exact  timing  of  the  spark  is  effected,  nor  the  means 


FIG.  24. 

adopted  to  enable  the  dynamo  coil  to  adapt  itself  to 
variations  in  the  speed  of  the  engine.  In  this  figure 
A  is  a  soft  iron  wire  bundle,  which  serves  at  once  as 
the  core  of  the  coil  and  as  the  field-magnet  of  the 
dynamo  ;  F  F  show  the  position  of  the  coarse-wire 
winding,  which  renders  the  machine  at  once  an 
efficient  series-wound  dynamo,  and  imparts  magnetism 
to  the  core  as  in  an  induction  coil.  Thence  the  wire 
is  led  to  the  brushes  1 1,  whence  the  current  generated 
by  the  armature  D  is  picked  up.  J  is  the  commutator, 


68      VARIOUS  METHODS  OF  IGNITION. 

G  G  are  the  secondary  coils,  the  terminations  of  which 
are  brought  out  at  H  H.  (In  the  modern  type  of 
dynamo  coil  only  one  wire  is  required  for  connection 
to  firing  plug.)  A  condenser  K  is  in  shunt  with  the 
primary  winding. 

It  will  be  evident  that  as  long  as  the  potential  of 
the  current  flowing  round  the  core  A  remains  the 
same,  no  current  will  be  generated  in  G  G  ;  but  if  any 
interruption  be  made  in  the  primary  circuit,  a  heavy 


FIG.  25. 


flash  will  occur  between  the  points  of  the  sparking 
plug  attached  to  the  terminals  H  H.  No  vibrating 
contact-breaker  is  required  ;  a  simple  plunger,  P,  Fig. 
25,  which  is  affixed  as  a  kind  of  stud  to  one  side  of  the 
dynamo-coil  base,  and  which  is  actuated  by  the  half- 
speed  cam,  serves  to  break  contact,  and  this  act  of 
breaking  contact  can  be  timed  with  the  greatest 
nicety,  so  as  to  insure  firing  at  the  most  opportune 
moment.  Figs.  25  and  26  are  side  and  back  eleva- 


VARIOUS  METHODS   OF  IGNITION.      69 

tions  of  the  perfected  forms  of  the  dynamo-coil.  The 
base  is  an  aluminium  case,  containing  the  condenser 
and  fitted  with  the  plunger  P,  and  a  bolting-down 
lug  on  each  side.  This  bears  upon  it  the  dynamo 
carcass,  surmounted  in  its  turn  by  the  "  coil  "  portion. 
To  the  left  of  Fig.  25  are  seen  the  bearings,  the 
driving  gear,  and  the  lubricator — the  right  hand 
showing  the  commutator  and  brush  end  of  the 
machine.  The  only  wire  necessary  for  connection  to 


FIG.  26. 

firing  plug  is  seen  attached  to  the  plug  at  the  top  of 
the  coil. 

The  idea  embodied  in  the  dynamo-coil  has  been 
largely  taken  up  by  different  makers  of  ignition 
devices,  and  has  resulted  in  the  production  of  "  high- 
tension  magnetos."  In  these  machines  the  accu- 
mulator, or  primary  battery,  as  a  means  of  exciting 
the  coil,  is  entirely  discarded,  and  the  coil  itself  (if 
separate)  is  not  furnished  with  a  vibrating  contacttj 


70       VARIOUS  METHODS   OF  IGNITION. 

breaker,  but  is  called  into  action  at  the  instant 
that  the  current,  set  up  by  the  coarse  wire  (or 
"  primary  ")  winding  of  the  armature,  has  reached  its 
point  of  maximum  intensity,  and  which  is  caused 
to  coincide  with  the  correct  time  for  firing  the 
gaseous  mixture  in  the  explosion  chamber,  by  means 
of  a  suitable  contact  or  "  plunger."  In  some  of 
these  high-tension  magnetos  the  coil,  or  secondary,  is 
entirely  distinct  and  separate  from  the  armature 
with  its  coarse-wire  winding  ;  as,  for  instance,  in 
the  "  Eisemann  "  ;  while  in  others,  as,  for  example, 
the  "  Simms  Bosch"  Arc  Light,  the  "  Gianoli,"  etc., 
the  secondary  winding,  which  constitutes  the  true  coil 


or  "  high-tension  "  portion  of  the  machine,  is  wound 
over  the  primary  of  the  armature.  In  either  mode  of 
construction  a  "  condenser,"  to  take  up  the  "  extra  " 
current  set  up  in  the  coils  of  the  primary  winding,  is 
an  absolute  necessity,  to  ensure  effective  sparking. 

Leaving  the  description  of  the  mode  of  con- 
structing the  coil  and  the  condenser  for  future 
consideration,  we  give  as  examples  of  the  "  high- 
tension  "  magneto  system  a  brief  description  of  the 
"  Eisemann,"  the  "  Simms  Bosch,"  and  the  "  Gianoli," 
as  being  typical  of  machines  of  this  class. 

The  Eisemann  was  the  first  of  the  "  high-tension  " 
magnetos  to  be  put  on  the  market,  and  differs  from 


VARIOUS  METHODS  OF  IGNITION.       71 

most  of  its  successors,  inasmuch  as  it  has  a  separate 
coil,  which  is  used  to  transform  the  low-tension 
current  set  up  by  the  armature  into  one  of  sufficiently 
high  tension  to  actuate  the  ordinary  sparking  plug. 
By  this  means  a  very  large  current  can  be  obtained, 


FIG.  28. — THE  EISEMANN  MAGNETO 


M,  Magnets. 

C,  Platinum  points. 

K,  Adjusting  nut. 

S,  Timing  disc. 

N,  Steel  cam. 


H,  Mark  on  timing  disc  which 
corresponds  with  a  similar 
mark  on  the  body  of  mag- 
neto when  timing  disc  is 
in  advanced  position. 


since  the  whole  of  the  armature  channel  can  be  filled 
with  stout  copper  wire  (see  Fig.  27),  and  no  space  is 
taken  up  by  any  finer  wire,  which  is  not  only  more 
difficult  to  insulate  properly  (on  an  armature),  but 
does  not  give  so  hot  a  spark.  Another  speciality 


72       VARIOUS  METHODS  OF  IGNITION. 

of  this  system  lies  in  the  arrangement  of  the  contact- 
breaker,  which  is  in  parallel  with  the  primary  winding 
of  the  coil,  instead  of  being,  as  in  other  makes,  in 
series  with  it.  This  allows  a  larger  current  to  be 
obtained  from  the  armature,  since,  as  the  resistance 
of  the  primary  winding  of  the  coil  is  cut  out,  a 
larger  current  can  flow.  This  arrangement  of  the 
contact-breaker  in  parallel  favours  the  production  of 
a  much  more  powerful  spark  ;  because,  as  the  spark 
occurs  when  the  current  flows  through  the  coil,  and 
not  when  it  ceases,  advantage  is  taken  of  the  fact 
already  mentioned  of  the  production  of  the  "extra" 
current  to  increase  the  volume  of  the  current  passing 
through  the  coil  when  the  platinum  contacts  are 
separated. 

At  Fig.  28  we  give  a  general  view  of  this  magneto, 
adapted  to  use  with  single  cylinder  engines.  For 
engines  with  two,  four,  or  more  cylinders,  the  Eise- 
mann  magnetos  are  similar  in  general  construction, 
but  larger  and  more  powerful,  and  are 'also  fitted  with 
a  high-tension  distributor.  The  armature  cannot  be 
seen,  as  it  lies  between  the  lower  extremities  of 
the  limbs  of  the  magnets  m.  The  cam  n  causing  the 
"  makes  "  and  "  breaks  "  is  carried  on  the  armature 
shaft.  The  platinum  points  are  situate  at  c,  and  one 
of  the  nuts,  by  means  of  which  they  may  be  adjusted, 
is  shown  at  k.  The  timing  disc  (shown  separately  on 
a  larger  scale  at  Fig.  30)  can  swing  through  an  angle 
of  29°,  which  is  sufficient  to  allow  the  spark  to 
be  advanced  or  retarded  to  the  greatest  required 
extent.  At  Fig.  29  is  given  an  illustration  of  an 
Eisemann  magneto  with  "  distributor "  (seen  just 
.below  H),  suitable  for  a  four-cylinder  engine.  The 


VARIOUS  METHODS  OF  IGNITION.       73 


field  magnets  consist  of  six  horseshoe  magnets 
screwed  to  soft-iron  pole  pieces,  which  embrace  the 
armature,  without  quite  touching  it,  for  about  three- 
quarters  of  its  total  diameter,  half  on  each  side.  The 
clearance,  in  order  to  secure  great  efficiency,  is  hardly 
more  than  the  thickness  of  a  sheet  of  writing-paper. 
The  armature,  shown  at  Fig.  27,  which  rotates  between 


FIG.  29. 


these  pole  pieces,  is  of  the  Siemen's  H  type.  On 
being  rotated  while  in  this  position  an  electric  current 
is  set  up  in  its  coils.  This  current,  as  we  have  seen, 
is  not  a  steady  one,  but  rises  to  a  maximum  and  falls 
to  zero  twice  during  every  revolution.  The  "  break  " 
of  the  primary  circuit  is  arranged  so  that  it  shall  take 
place  when  the  current  is  near  its  maximum.  The 


74       VARIOUS  METHODS   OF  IGNITION. 


two  ends  of  the  armature  spindle  (see  Fig.  27)  are 
separate,  and  are  screwed  into  the  brass  end-plates  of 
the  armature.  The  spindle  runs  in  long  bearings  in 
brass-bearing  plates.  These  are  furnished  with  suffi- 


FIG.  30. 

C,  Copper  plug  on  armature  shaft. 

SC,  Steel  earn. 

BN,   Brass  nut  holding. 

SBT,  Springy  brass  tongues. 

TD,  Timing  disc. 

FS,  Forked  steel  piece. 


P,   Pin  working  in  slot,  S. 

A  and  B,  Steel  pins. 

CS,  Contact  spring  held  by  N,  nut, 

and  SP,  split  pin. 
oc,  Oil  cup. 
ASL,  Advance  spark  lever. 


cient  lubrication,  a  small  hole  being  provided  for 
surplus  oil,  so  as  to  prevent  its  reaching  any  part 
where  its  presence  might  be  harmful.  The  timing 
disc  is  shown  separately  at  Fig.  30  with  the  contact- 


VARIOUS  METHODS  OF  IGNITION.      75 


,  .  _*-J»., 


FIG.  31. 


76      VARIOUS  METHODS  OF  IGNITION. 

breaker  removed,  and  is  eccentric  to  the  armature 
bearing,  about  which  it  turns.  The  pin  P  in  the 
bearing  plate  passes  through  the  slot  s,  the  length  of 
which  limits  the  extent  of  "  advance  "  or  "  retard  "  of 
firing. 

When  used  on  2,  3,  4,  and  6  cylinders,  these  mag- 
netos have  the  advance  and  retard  arranged  in  a 
different  manner,  by  means  of  a  pin  working  in  a 
diagonal  slot,  with  a  sleeve  over  the  same,  upon 
which  the  driving  sprocket  is  fixed  (see  the  two 
illustrations  forming  Fig.  31).  The  springy  brass 


FIG.  32. 

tongues,  SET  (Fig.  30),  press  the  timing  disc  against 
the  bearing  plate,  and  are  themselves  secured  by 
a  nut  on  the  outside  of  the  bearing.  The  steel  cam, 
S  C,  rotates  with  the  armature  shaft.  One  end  of  the 
armature  coil  (or  wiring)  passes  through  the  centre 
of  the  shaft  and  makes  contact  with  the  copper  plug, 
C,  which  protrudes  from  the  end  of  the  shaft  ;  from 
which,  however,  it  is  insulated  by  means  of  fibre. 
The  forked  steel  piece,  F  S,  makes  good  contact  be- 
tween the  shaft  and  the  steel  pin,  A,  its  ends  bearing 
upon  the  inside  of  the  cam,  S  C.  This  forked  piece  is 
shown  separately  at  Fig.  32. 


VARIOUS   METHODS   OF  IGNITION.      77 

We  can  now,  by  the  aid  of  Fig.  33,  form  some  idea 
of  the  connection  and  working.  One  end  of  the 
armature  coil,  or  wiring,  is  "  earthed  "  to  the  machine, 
and  the  other  end  is,  as  we  have  just  stated,  brought 
out  through  the  armature  spindle,  and  is  in  electrical 
connection  with  one  of  the  platinum  points,  P,  which 
is  insulated  from  the  frame.  Near  this  spot  the  wire, 


PW 


PW,  leading  to  the  primary  of  the  coil,  is  taken  off. 
The  bell-crank  lever,  B  L  (see  also  Figs.  34  and  35), 
carrying  the  second  platinum  point,  P,  is  in  connec- 
tion with  the  frame  ;  hence,  while  these  points  are  in 
contact,  the  current  has  a  free  passage  to  "  earth," 
and  completes  its  circuit  at  the  "  earthed"  end  of  the 
armature.  The  lever,  B  L,  is  held  by  a  spring  against 
the  cam,  C  ;  which  cam  rotates  with  the  armature, 


78      VARIOUS  METHODS   OF  IGNITION. 

causing  the  necessary  "  makes  "  and  "  breaks  "  at  the 
platinum  points.  When  the  points,  P,  are  separated, 
the  earth  circuit  is  broken,  and  the  current  can  flow 
only  down  the  wire,  P  W,  through  the  coil,  and  thence 
through  the  frame  to  the  armature  :  this  can  only 
happen  when  the  switch,  S  (Fig.  33)  is  open,  as  in  the 
diagram.  When  it  is  closed  it  conducts  the  current 
to  earth  without  its  passing  through  the  coil.  It  will 


FIG.  34. 

BL,   Bell-crank  lever. 

P,     Platinum  contact. 

S,     Screw,  carrying  platinum. 


AN,  Adjusting  nut. 

R,      Roller. 

AR,  Axle  of  roller. 


be  noticed  that  even  when  the  switch,  S,  is  open,  the 
armature  itself  is  not  on  open  circuit.  On  the 
other  hand,  the  armature  current  flows  along  a 
path  of  very  low  resistance,  namely,  to  earth  ;  or, 
in  other  words,  the  armature  is  short  -  circuited. 
This  is,  in  fact,  its  normal  condition,  and  it  is, 
as  already  explained,  never  advisable  to  run  a 
magneto  on  open  circuit.  Under  running  con- 
ditions, with  the  switch  open,  there  is  a  permanent 


VARIOUS  METHODS   OF  IGNITION.       79 

connection  through  the  coil,  but  no  appreciable 
current  passes  this  way  until  the  points  r  arc 
separated.  This  is  due  to  the  fact  that  the  "  earth  " 
circuit  presents  far  less  resistance,  so  that  practically 
the  whole  current  takes  the  easier  route.  When,  under 
the  influence  of  the  cam,  C,  the  points,  P,  separate, 
there  is  consequently  a  sudden  rush  of  current  along 
the  only  path  left  open,  namely,  through  the  coil.  It  is 


FIG.  35. 

1C,  Insulated  casting  sw,  Nut  holding  spring. 

CP,  Carbon  pencil.  IR,    Insulating  rings. 

at  this  instant  that  the  spark  occurs  at  the  plug,  S  P 
(Fig.  33).  In  other  words,  the  spark  occurs  when  the 
current  begins  to  flow  through  the  coil,  and  not,  as  in 
an  accumulator  system,  when  it  ceases  so  to  do.  If 
the  switch  were  wired  in  the  usual  way,  and  the  switch 
opened,  the  armature  would  be  running  on  an  open 
circuit  for  a  part  of  every  revolution.  The  earth  circuit 
being  broken  when  the  armature  current  is  near  its 
maximum,  there  would  arise  violent  and  destructive 


8o      VARIOUS  METHODS   OF  IGNITION. 

sparking  at  the  platinum  points.  Careful  attention 
must  therefore  be  given  to  the  correct  wiring  of  the 
switch. 

By  the  aid  of  the  foregoing  explanations,  with  their 
accompanying  diagrams,  the  reader  can  easily  follow 
the  path  of  the  current,  which  is  as  follows  : — Starting 
from  the  end  of  the  armature  coil  which  is  insulated 
from  the  machine,  the  current  flows  along  the  copper 
plug,  C  (Figs.  30,  33,  34),  which  is  insulated  from  the 
armature.  Thence  it  passes  through  the  carbon 
pencil,  C  P  (Fig.  35),  and  the  spring  partly  seen 


FIG.  36. 

between  S  and  B  L  in  (Fig.  35),  till  it  reaches  the 
platinum  points,  C  (Fig.  28);  also  shown  at  Pin  Figs. 
33,  34,  and  35.  From  that  point,  when  the  platinum 
points  are  in  contact,  the  current  flows  across  them 
into  the  bell-crank  lever,  B  L  (Figs.  33,  34,  and  35), 
going  through  the  forked  steel  piece,  F  S  (Figs.  30 
and  32),  to  the  "earthed"  end  of  the  armature  coil, 
and  thus  completes  its  circuit. 

In  the  foregoing  description  the  reader  will  bear 
in  mind  that  the  term  "  earthed "  means  simply 
connected  electrically  to  the  uninsulated  body  of  the 
machine.  When  the  platinum  points,  P,  are  separated 


VARIOUS  METHODS   OF  IGNITION.      81 

the  current  has  no  other  path  open  to  it  from  the 
casting,  I  C  (Fig.  35),  except  through  the  wire  leading 
to  the  switch  or  induction  coil.  The  other  end  of  the 
primary  of  the  said  coil  being  "  earthed,"  the  current 
passes  to  the  frame,  back  to  the  magneto,  completing 
its  circuit  as  before.  The  connection  of  the  positive 
end  of  the  secondary  of  the  coil  to  the  sparking  plug 


FIG.  37. 
THE  SIMMS-BOSCH  "ARC  LIGHT  HIGH-TENSION  MAGNETO." 


is  shown  at  s  P  (Fig.  33),  the  negative  end  of  the 
secondary  being,  as  usual,  connected  to  frame,  or 
"  earthed."  The  general  appearance  of  a  sparking 
plug  (actual  size)  is  given  at  Fig.  36. 

We  may  now  pass  on  to  consider  the  Simms-Bosch 
"  Arc  Light "  magneto,  of  which  we  give  a  sectional 
view  at  Fig.  37,  showing  the  mode  of  connection  to 

F 


82       VARIOUS  METHODS   OF  IGNITION. 

distributor  and  plugs  when  used  with  a  four-cylinder 
engine.  Of  course,  if  there  be  only  one  or  two  cylin- 
ders to  fire,  the  distributor,  X,  will  be  furnished  with 
only  one  or  two  contacts  to  correspond.  The  timing 
gear  forms  an  integral  part  of  the  magneto,  the  lever 
of  which  is  operated  in  the  usual  manner  by  a  cam. 
The  armature,  A,  consists  as  usual  in  a  channeled 
cylinder  of  iron,  in  the  channel  of  which  are  two 
separate  and  independent  windings.  The  "primary" 
is  made  up  of  comparatively  few  turns  of  coarse  wire, 
wound  round  the  "  web  "  of  the  armature.  Over  this, 
or  even  alongside  of  it,  is  wound  the  "  secondary,"  con- 
sisting of  many  turns  of  fine  insulated  wire.  For  the 
sake  of  clearness  we  have,  in  our  illustration,  shown 
these  two  wirings  as  lying  alongside  one  another, 
instead  of  the  secondary  being  superimposed  on  the 
primary.  In  practice  it  is  immaterial  which  plan  is 
adopted,  provided  the  two  windings  be  perfectly 
insulated  from  one  another,  and  the  gauge  and 
quantity  of  wire  in  each  be  in  due  proportion. 

The  armature  is  stationary  in  the  tunnel  of  the  pole- 
pieces  of  three  powerful  compound  horseshoe  magnets. 
An  oscillating  iron  sleeve,  or  "  shield,"  slotted  at  its 
two  opposite  sides,  and  fitting  with  great  exactitude 
between  the  inside  of  the  tunnel  and  the  outside  of 
the  armature,  serves  alternately  to  shield  and  to 
expose  the  armature  to  the  lines  of  force  emanating 
from  the  magnet,  according  to  whether  the  sleeve,  by 
the  oscillatory  motion  imparted  to  it,  uncovers  or  covers 
the  wound  portion  of  the  armature.  Mounted  at  one 
end  of  the  armature  is  a  form  of  interrupter  or 
contact-breaker,  I,  D,  the  scope  of  which  is  to  break 
suddenly  the  primary  circuit,  at  the  instant  at  which 


VARIOUS  METHODS  OF  IGNITION.      83 

the  current  induced  therein  by  the  magnetic  flux 
reaches  its  maximum.  This  sudden  interruption  of 
the  primary  circuit  elicits  at  the  same  instant  a 
powerful  high-tension  current  in  the  secondary 
circuit.  One  end  of  each  winding  is  in  connection 
with  the  metal-work  of  the  machine  ;  the  other  ends 
are  passed  through  suitable  insulators  and  connected 
to  metal  rings,  whence  the  current  is  picked  up  by 
carbon  brushes,  and  passed  on  to  the  sparking  plug, 
P,  by  means  of  a  well-insulated  cable. 

As  the  secondary  winding  of  the  armature  forms 
practically  a  coil,  it  is  essential  to  the  efficient  working 
of  this  magneto  that  it  should  be  provided  with  a 
condenser^  C,  which  is  shown  in  our  illustration  in  the 
recess  just  above  the  armature.  It  is  connected  in 
the  usual  manner,  namely,  in  shunt  with  the  two 
halves  of  the  contact-breaker  or  interrupter,  on  the 
primary  circuit.  To  prevent  any  injury  to  the 
primary  circuit,  in  the  event  of  the  connection 
between  sparking  plug  and  secondary  becoming 
broken,  a  device,  known  as  a  "  safety-spark  gap,"  G, 
is  arranged  on  the  secondary  circuit,  which  serves  as 
a  safety-valve  against  any  excessive  generation  of 
current. 

The  next  magneto  to  claim  our  attention  is  the 
"  Gianoli,"  which  embodies  a  modification  in  the 
mode  in  which  the  circuit  is  suddenly  broken,  that 
renders  it  worthy  of  separate  notice.  As  is  usual 
with  high-tension  magnetos,  the  machine  consists 
essentially  of  a  set  of  magnets  with  pole-pieces,  and  an 
armature  wound  with  two  separate,  well-insulated 
and  independent  windings,  of  which  the  inner,  or  one 
nearer  the  core,  is  of  comparatively  coarse  wire,  and 


84       VARIOUS  METHODS  OF  IGNITION. 

constitutes  the  primary  ;  while  the  exterior  layers, 
which  occupy  about  twice  the  space  of  this  primary, 
consist  of  numerous  turns  of  fine  wire,  and  form  the 
secondary.  The  usual  minor  fittings,  as  used  in  other 
magnetos,  are  also  present,  such  as  contacts,  insulators, 


FIG.  38.— THE  "GIANOLI"  HIGH-TENSION  MAGNETO. 

terminals,  main  shaft  bearings,  lubricators,  etc.,  and 
are  clearly  shown  in  our  sectional  illustration,  Fig.  38. 
But  the  "  Gianoli "  magneto  differs  in  two  main 
features  from  those  previously  described,  inasmuch 
that,  firstly, the  interruption  or  "break"  in  the  circuit 
is  effected  automatically  by  the  effect  of  the  induced 


VARIOUS  METHODS   OF  IGNITION.      85 

magnetism  in  the  core  of  the  armature,  without 
needing  any  mechanical  device  or  springs  ;  and, 
secondly,  the  manner  in  which  the  advancement  or 
retardation  in  the  ignition  is  governed,  by  shifting 
the  pole-pieces  through  a  given  angle  of  an  arc  by 
means  of  a  "  timing  "  lever — this  having  the  effect  of 
moving  the  magnetic  field  (and  consequently  the 


FIG.  39. 

lines  of  force)  into  another  position,  as  may  be 
required.  The  mode  in  which  the  "  automatic 
interrupter "  operates  is  shown  in  Fig.  39.  A  thin 
plate  of  soft  iron,  which  plays  the  same  part  as  the 
iron  bob  in  the  contact-breaker  of  an  ordinary  in- 
duction coil,  is  attached  to  one  extremity  of  a  light 
spring.  In  front  of  this  latter  is  another  spring, 


86      VARIOUS  METHODS   OF  IGNITION. 

bearing  at  its  end  (a  little  above  the  soft-iron  plate) 
a  platinum  contact-tip.  Both  these  springs  are  held 
in  place  in  front  of  the  cheeks  of  the  armature  by  a 
screw  common  to  both,  as  shown  near  the  bottom,  to 
the  left  of  Fig.  39.  The  platinum-tipped  spring 


FIG.  40. 

in  its  normal  condition  rests  against  an  adjustable 
platinum-tipped  contact-screw,  thus  completing  the 
primary  circuit.  The  wound  armature  is  provided 
with  small  soft-iron  polar  extensions  (one  of  which  is 
shown  in  the  illustration,  facing  the  upper  end  of  the 
spring  and  iron  bob).  When  the  armature  rotates 


VARIOUS  METHODS  OF  IGNITION.       87 

it  becomes  magnetised  by  the  inductive  influence  of 
the  field-magnets,  and  when  the  polar  extensions  are 
facing  the  iron  bob  (which  is  made  to  correspond 
with  the  point  of  maximum  electrical  intensity),  the 
iron  bob  is  strongly  attracted,  and  strikes  against  the 
inner  surface  of  the  outer  spring.  This  causes  an 
instantaneous  rupture  between  the  two  platinum 
contacts,  thereby  setting  up  a  powerful  current  in  the 
secondary,  which  current  is  led,  in  the  usual  manner, 
to  the  sparking  plug  or  plugs.  This  attraction  of  the 
iron  plate  or  bob  is  rapid  at  all  speeds,  and  corres- 
ponds with  the  instant  at  which  the  highest  electrical 
tension  is  set  up  in  the  armature  wires,  thus  producing 
a  succession  of  sparks  at  each  "  maximum  "  period 
or  phase  of  the  armature's  rotation.  This  enables 
starting  to  be  easily  accomplished. 

Another  important  advantage  is,  that  no  matter 
how  fast  the  armature  may  be  driven,  it  is  impossible 
for  an  excess  of  current  to  be  generated,  thus  avoiding 
injury  to  the  armature  winding,  or  necessity  of  having 
a  "safety"  spark  gap.  In  fact,  the  iron  plate  vibrator 
acts  as  a  perfect  electro -magnetic  governor,  and 
always  breaks  the  circuit  at  the  same  voltage, 
irrespective  of  speed. 

The  position  of  the  movable  pole-pieces,  with  the 
means  adopted  to  carry  them  through  the  desired 
number  of  degrees  of  arc,  to  secure  advancement  or 
retardation  of  firing,  the  polar  extensions  of  armature, 
that  serve  to  attract  the  plate  or  "  bob,"  are  well 
shown  in  our  Fig.  40. 


CHAPTER   III. 
PRIMARY  AND  SECONDARY  COILS. 

THERE  can  be  but  little  doubt,  in  view  of  the 
experience  gained  during  the  last  few  years, 
in  driving  automobiles,  whether  large  or 
small,  that  instruments  of  the  class  just  described 
—viz.,  those  in  which  the  necessary  sparking  current 
is  obtained  from  a  dynamo,  having  either  permanent 
magnets  ("  magnetos ")  or  temporary  ones  ("  dyna- 
mos")— constitute  at  once  the  most  efficient,  the 
lightest,  and  most  satisfactory  means  of  securing  the 
ignition  of  the  gaseous  mixture  in  the  combustion 
chamber.  But  there  are  many  engines,  both  sta- 
tionary and  mobile,  which  are  fitted  with  coils  ;  and 
many  of  our  readers  may  have  occasion  to  use,  to 
repair,  or  even  to  make  coils  suitable  for  this  pur- 
pose. Hence  a  general  description,  followed  by  a  few 
hints  as  to  construction,  will  be  acceptable. 

For  the  purpose  under  consideration  coils  may  be 
divided  into  two  classes,  viz.,  (i)  those  wound  with 
one  continuous  length  of  wire  ;  (2)  those  in  which 
there  are  two  separate  windings — one  of  a  com- 
paratively coarse  wire,  called  x' the  primary,"  and 
another  of  finer  wire  known  as  "  the  secondary." 
Those  of  the  first  class,  or  "  simple  primary,"  can 
(speaking  generally)  only  be  employed  where  a 
'wiping  contact  is  admissible,  and  therefore  we  shall 
dismiss  them  with  a  very  brief  notice.  Coils  of  the 
second  class  can  be  subdivided  into  those  which  have 


PRIMARY  AND  SECONDARY  COILS.      89 

a  vibrating  contact-breaker  as  an  essential  portion  of 
the  coil,  and  those  in  which  the  make  and  break  of 
the  contact  is  effected  by  some  mechanical  device, 
actuated  by  a  cam  on  the  engine  itself. 

The  principle  of  action  of  the  coil  is  very  simple, 
and  although  during  the  work  of  a  coil  there  are  con- 
comitant actions  going  on  which  somewhat  com- 
plicate matters,  it  will  not  be  necessary  for  our 
purpose  to  go  very  deeply  into  these  points. 

The  first  fact  that  claims  our  attention  is,  that  if 
we  take  a  length  of  wire  and  coil  it  into  a  helix, 
a  momentary  current  sent  through  the  helix  sets  up 
two  actions,  (i)  On  making  contact  with  source  of 
current,  a  momentary  current  in  the  opposite  direction 
to  the  main  current  is  set  up  in  the  wire.  But  as  this 
current  is  only  transient,  and  weaker  than  the  main 
current,  its  presence  can  only  be  detected  by  the 
momentary  weakening  of  the  main  current.  (2)  On 
breaking  contact  with  the  source  of  current,  another 
wave  of  current  is  set  up  in  the  helix — this  time  in 
the  same  direction  as  that  of  the  main  current. 

It  must  be  particularly  noted  that  these  effects  are 
transient,  and  produced  at  the  instants  of  "  making  " 
and  "  breaking "  contact  only,  and  are  not  in  evi- 
dence while  the  main  current  is  flowing.  The  cur- 
rents thus  set  up  were  originally  called  "  extra " 
currents,  but  are  now  known  by  the  more  appropriate 
one  of  "  self-induction  currents."  Each  turn  of  the 
helix  has  a  given  E.M.F.  induced  in  it,  so  that  the 
resulting  E.M.F.  is  proportional  to  the  number  of 
turns  in  the  helix,  multiplied  by  the  original  E.M.F.  ; 
but  since  we  cannot  produce  energy,  but  only  change 
its  form,  we  find  that  the  volume  of  current  (the 


90      PRIMARY  AND   SECONDARY  COILS. 

amperes)  is  diminished  in  like  ratio.  So  that  if 
we  supply  a  current  of  I  ampere  at  I  volt  pressure  to 
a  coil  consisting  of  1,000  turns  of  wire,  we  may 
expect,  when  breaking  circuit,  to  get  a  momentary 
current  of  TirVo-  °f  an  ampere,  at  1,000  volts  pressure, 
less,  of  course,  a  certain  amount  of  loss  due  to  the 
conversion  of  part  of  the  energy  into  heat,  and 
dissipation  of  the  magnetic  field,  etc.  The  second 
point  that  demands  attention  is  that  if  two  distinct 
wires  lie  side  by  side,  but  not  in  electrical  contact, 
and  momentary  contact  be  made  with  any  source 
of  current  and  one  of  the  wires,  a  similar  transient 
current  will  be  set  up  in  the  adjacent  wire,  but  in  the 
opposite  direction  to  that  of  the  inducing  current. 
Owing  to  the  damping  effect  of  the  "  make  "  self- 
induced  current  in  the  first  wire,  the  "  make " 
induced  current  in  the  second  wire  is  not  very  strong. 
On  breaking  contact  between  the  source  of  current 
and  the  first,  or  "  primary  "  wire,  a  second  momentary 
current  is  set  up  in  the  second  (or  "  secondary  ")  wire. 
But  this  is  now  in  the  same  direction  as  the  originally 
"  primary  "  current  was,  and  since  it  is  not  checked 
by  any  counter- effect  from  the  primary,  the  resulting 
"  break-contact  "  current  is  much  more  powerful  than 
the  corresponding  "  make-contact  "  current  was. 

It  will  be  evident  that  if  we  coil  the  primary  wire 
into  the  shape  of  a  tight  helix,  and  surround  this 
with  a  large  number  of  convolutions  of  secondary 
wire,  we  can  exalt  the  E.M.F.  (lowering  in  like  degree 
the  volume  of  current  in  amperes)  to  almost  any 
desired  extent,  dependent  on  the  ratio  between  the 
number  of  turns  on  primary  and  secondary  respec- 
tively. If,  instead  of  winding  the  primary  wire  into 


PRIMARY  AND   SECONDARY  COILS.      91 

a  coil  without  any  core,  we  wind  it  upon  a  core 
of  soft  iron,  as  this  latter  will  concentrate  the  mag 
netic  field,  instead  of  allowing  it  to  stray,  we  shall 
largely  increase  the  induction  effect,  both  on  primary 
and  secondary  windings.  We  are  now  in  a  position 
to  understand  what  is  essential  to  the  production  of  a 
good  sparking  coil,  whether  "  simple  primary "  or 
"  secondary." 

In  the  first  case  we  require  a  soft  iron  core,  to  con- 
centrate the  magnetic  field  set  up,  overwound  with  a 
sufficient  number  of  turns  of  insulated  wire  to  raise 
the  E.M.F.  set  up  by  the  battery  to  a  sufficient 
degree  to  enable  it  to  produce  a  spark  of  the  length 
desired  ;  and,  lastly,  some  device  for  making  and 
breaking  contact  between  the  battery  and  the 
primary  at  the  time  and  the  place  where  the  spark 
is  required.  In  the  second  case,  besides  the  iron  core, 
the  primary,  and  the  contact-breaker,  we  require  some 
means  of  taking  up  the  self-induced  current,  which 
we  cannot  in  this  case  utilise,  and  which  is  actually 
detrimental  to  the  efficient  working  of  the  secondary. 
Over  this  primary  we  must  have  a  sufficient  number 
of  turns  of  a  finer  secondary  wire,  entirely  separate 
and  insulated  from  the  primary,  to  set  up  an  in- 
duced E.M.F.  sufficiently  high  to  produce  a  spark 
of  the  desired  length.  For  this  case  also  we  must 
have  a  means  of  making  and  breaking  contact  with 
the  battery,  accumulator,  or  other  source  of  current. 
This  second  form  of  coil  differs,  however,  from  the 
first,  inasmuch  as  the  contact-breaking  arrangement 
is  quite  independent  of  the  place  at  which  the  spark  is 
produced,  so  that  the  contact  need  not  be  made  and 
broken  at  the  spot  where  the  ignition  is  required. 


92      PRIMARY  AND   SECONDARY  COILS. 

The  following  details  as  to  dimensions,  gauge  of 
wire,  and  general  mode  of  construction,  may  be  useful 
to  those  desirous  of  building  a  "  primary  "  coil,  suit- 
able for  gas  or  petrol-vapour  ignition.  It  should  be 
noted  that  this  type  of  coil  is  suitable  only  for  those 
cases  in  which  the  act  of  "  contact-breaking  "  can  be 
effected  at  the  spot  where  ignition  is  desired. 

A  couple  of  hard-wood  heads  (oak  or  beach),  4  ins. 
square  by  I  in.  thick,  should  be  planed  up,  and  soaked 
for  some  time  in  melted  paraffin  wax.  Through  the 
centre  of  these  a  hole  f  in.  in  diameter  must  be  put. 
A  bundle  of  perfectly  straight  soft  iron  wire,  No.  22 
B.W.G.  (carefully  annealed  in  the  fire,  and  allowed  to 
cool  slowly  in  the  ashes),  is  now  to  be  made  up  into 
a  cylindrical  core,  12  ins.  long,  f  in.  diameter.  The 
simplest  way  of  doing  this  is  to  get  a  couple  of  curtain 
rings  |  in.  inside  diameter,  and  having  made  up  a 
bundle  of  wires  nearly  the  desired  size,  place  a  ring 
on  each  end,  at  about  \  in.  from  each  extremity,  then 
cautiously  push  in  more  wires  until  the  whole  is  firm 
and  solid. 

A  piece  of  i-in.  wide  tape  is  now  taken  and  wrapped 
spirally  from  end  to  end,  as  tightly  as  ever  it  can  be 
drawn,  and  the  termination  stitched  down  to  the  layer 
below,  so  as  to  prevent  uncoiling.  Any  excess  of 
tape  can  now  be  cut  of  and  the  rings  removed.  Over 
the  completed  core  it  will  be  advisable  to  roll  and  paste 
down  one  turn  of  stout  brown  paper,  which  should  be 
rolled  with  a  flat  board  on  a  flat  table,  so  as  to  cause 
it  to  lay  tightly,  flatly,  and  smoothly.  This  being  done, 
the  core  is  allowed  to  dry  thoroughly,  after  which  it 
should  be  allowed  to  simmer  in  hot  melted  paraffin 
wax  until  no  more  bubbles  appear  ;  then  reared  up  on 


PRIMARY  AND   SECONDARY  COILS.      93 

end  to  drain  and  cool.  When  cold,  the  core  is  fitted 
and  glued  into  the  holes  in  the  wooden  heads  (these 
being  slightly  enlarged  by  rubbing  round  with  a  cir- 
cular stick  covered  with  sandpaper,  if  necessary). 
The  ends  of  the  core  should  come  up  flush  with  the 
outside  faces  of  the  heads,  and  in  order  to  insure  a 
perfectly  rigid  fit,  it  may  be  advisable  to  drive  two  or 
three  short  lengths  of  the  No.  22  iron  wire  into  the 
centre  of  the  core  at  each  end,  so  as  to  swell  it  at  these 
points.  Care,  of  course,  must  be  taken  that  the  heads 
stand  perfectly  square  and  parallel  to  each  other.  A 
small  hole  (about  TV  in.  diameter)  to  allow  of  the 
passage  of  No.  18  double  cotton-covered  copper  wire, 
is  now  drilled  through  one  of  the  heads,  close  to,  but 
not  touching,  the  core.  Through  this  hole  is  pushed 
from  the  inside  about  3  ins.  of  a  4-lb.  hank  of  No.  18 
double  cotton-covered  copper  wire,  and  the  core 
wound  evenly  from  end  to  end.  As  this  wire  is 
pliable,  and  not  too  fine  to  handle,  the  winding  may 
be  done  by  hand  with  perfect  ease  ;  but  it  may  be  done 
more  quickly  if  the  core  be  set  up  between  centres 
and  rotated  while  the  wire  is  being  gently  pulled. 
Care  must  be  taken  to  wind  the  wire  on  evenly  and 
closely,  so  as  to  leave  no  spaces  between  the  rows. 

When  one  layer  has  been  laid  on,  the  wire  should 
be  fastened  back,  or  held  by  an  assistant,  so  that  it 
should  not  uncoil,  and  the  layer  then  basted  with  hot 
melted  paraffin  wax,  any  excess  being  melted  off  by 
passing  over  the  surface  of  the  layer  with  a  strip  of 
hoop-iron,  about  f  in.  wide,  made  sufficiently  hot  to 
melt  the  paraffin  wax,  but  not  to  burn  it. 

Winding  always  in  the  same  direction,  but  return- 
ing towards  the  head  at  which  the  start  was  made,  a 


94      PRIMARY  AND   SECONDARY  COILS. 

second  layer  of  wire  is  now  put  on,  with  all  the  pre- 
cautions indicated  above.  This  is  also  paraffined, 
and  the  winding  and  basting  continued  in  like  manner 
until  the  whole  of  the  wire  has  been  wound  on,  which 
will  take  about  seventeen  layers.  Care  should  be 
taken  to  terminate  with  an  odd  number  of  layers,  so 
as  to  get  the  finishing  end  of  the  wire  close  to  the 
head  opposite  to  that  from  which  the  start  was  made. 
A  hole  is  now  made  in  the  head  at  this  point  in  a  line* 
with  the  other  hole,  the  wire  end  pulled  through  to 
the  outside,  and  cut  off  at  a  distance  of  about  3  ins. 
from  the  face  of  this  head. 

A  few  sheets  of  demy  paper  are  now  prepared  by 
dipping  in  melted  paraffin  wax  and  hanging  up  to 
drain.  When  cold,  these  are  cut  into  strips  about 
1 8  ins.  long  and  of  sufficient  width  to  lie  exactly 
between  the  heads  of  the  coil.  About  six  of  these 
strips  are  now  bound,  one  after  the  other,  tightly  round 
the  last  layer  of  the  wire  and  fastened  down  by  warm- 
ing the  last  edge  with  the  hot  hoop-iron  strip,  so  as 
to  cause  the  paraffin  to  melt  and  stick.  Over  this,  as 
a  finish,  one  turn  of  sheet  ebonite  (-g^in.  thick)  should 
be  rolled  round,  little  holes  being  made  in  the  oppos- 
ing edges  with  a  hot  wire,  and  then  stitched  together 
with  a  suitable  length  of  strong  black  silk  twist.  Two 
holes,  to  take  the  screw-shanks  of  two  terminals,  are 
now  drilled,  one  in  the  centre  of  the  edge  of  each 
of  the  heads,  nearest  the  projecting  wire  ends.  The 
wires  are  straightened  out,  bared  of  their  covering, 
and  cleaned  bright  with  a  bit  of  emery  cloth,  looped 
once  round  the  stem  of  the  corresponding  terminal, 
which  is  then  screwed  up  tight.  The  excess  of  wire 
is  now  cut  off  flush  with  the  terminal. 


PRIMARY  AND  SECONDARY  COILS.     95 

The  coil  may  now  be  tested  by  connecting  one 
terminal  to  a  wire  from  one  pole  of  a  2-volt  accumu- 
lator, or  a  couple  of  large  dry  cells  coupled  in  series  ; 
then  quickly  making  and  breaking  contact  with  the 
other  terminal  by  means  of  a  second  wire  proceeding 
from  the  other  pole  of  the  accumulator.  A  bright  and 
heavy  flash  should  appear  each  time  contact  is  broken. 
Care  should  be  taken,  in  making  these  trials,  not  to 
leave  the  battery  connected  with  the  coil,  because,  as 
the  resistance  of  the  wire  on  it  is  but  low  (about  2 
ohms),  the  battery  would  soon  be  run  down. 

It  will  be  readily  understood  that  the  form  of  such 
a  coil  may  be  somewhat  varied  to  suit  the  exigencies 
of  space,  convenience  of  stowage,  etc.  The  heads 
may  be  round  instead  of  square,  and  the  coil  may  be 
made  only  6  ins.  long  instead  of  12  ins.,  the  winding 
being  effected  with  No.  20  wire  instead  of  No.  18, 
provided  about  2,500  turns  be  got  on  the  core.  To 
work  such  a  coil,  any  cell  capable  of  sending  about 
2  amperes  through  will  cause  it  to  give  a  good  heavy 
flash,  capable  of  firing  the  gaseous  mixture.  The 
best  cell  to  employ  for  the  purpose  is  undoubtedly  a 
4-volt  accumulator,  of  about  14  ampere-hour  capacity. 

We  now  proceed  to  show  the  means  which  may 
be  adopted  to  effect  the  firing  of  the  gaseous  mixture 
at  the  right  time  and  place  when  a  "  primary  "  coil, 
such  as  described  in  our  last  few  sections,  is  employed. 
The  simplest  means  which  may  be  used  in  stationary 
oil  or  gas  engines  consists  in  connecting  up  the  body 
of  the  cylinder  to  the  negative  wire  of  the  coil,  and 
arranging  a  platinum-faced  L-shaped  brass  piece, 
pivoted  at  the  bend,  which  wipes  across  a  wire  or  a 
nipple  situated  just  in  front  of  a  hole  in  the  combus- 


96      PRIMARY  AND  SECONDARY  COILS. 

tion  chamber.  This  L-piece  is  in  circuit  with  the 
battery  and  the  other  wire  of  the  coil,  and  is  caused 
to  "  wipe  "  across  the  nipple  by  means  of  a  cam  con- 
nected to  any  rotating  portion  of  the  engine.  To 
bring  this  L-piece  into  the  "off"  position  after  having 
received  the  push  from  the  cam,  it  is  furnished  with  a 
counter-spring.  Of  course,  the  cam  must  be  set  in 
such  a  position  as  to  insure  the  spark  being  produced 
at  the  right  instant. 

Another  simple  means  consists  in  inserting  a  porce- 
lain plug  in  the  ignition-chamber  of  the  cylinder,  this 
plug  bearing  up  its  centre  two  wires,  insulated  from 
each  other  and  projecting  into  the  cylinder,  one  shorter 
wire  terminating  in  a  platinum  stud,  and  the  other 
bearing  a  platinum-tipped  spring.  This  plug  is  in- 
serted in  the  cylinder  in  such  a  position  that,  when  the 
piston  has  reached  the  point  of  greatest  compression, 
it  pushes  the  platinum -tipped  spring  against  the 
platinum  stud,  thus  completing  the  circuit  between  the 
battery  and  coil,  wires  from  which  are  connected  to 
the  externally-protruding  wires  (or,  better,  terminals) 
of  the  porcelain  plug.  Directly  the  piston  has  passed 
the  dead-point,  and  begins  to  travel  outwardly,  con- 
tact is  broken  between  the  platinum-tipped  spring. 
Hence  a  spark  is  produced  in  the  combustion  chamber, 
and  the  charge  is  fired. 

The  great  defect  in  these  two  modes  of  firing  is  the 
difficulty  of  timing  the  spark  while  the  engine  is  in 
motion.  Now  this  power  of  timing  the  spark  (and, 
consequently,  the  explosion)  is  a  matter  of  the  highest 
importance,  especially  for  motor  car  and  cycle  work, 
in  which  the  speed  and  power  may  have  to  be  sud- 
denly and  largely  varied. 


PRIMARY  AND  SECONDARY  COILS.      97 

Let  us  suppose,  for  the  sake  of  example,  that  the 
explosions  were  made  to  take  place,  in  starting  the 
engine,  when  the  piston  is  at  the  beginning  of  its 
inward  stroke,  with  its  crank  quite  straight,  or  at  the 
"  dead-point."  It  is  evident  that  the  piston  could  not 
move  :  consequently,  the  explosion  would  only  strain 
the  firing  chamber,  and  do  nothing  else.  Therefore 
it  is  essential,  in  starting  the  engine,  that  the  explosion 
should  not  take  place  until  the  piston  has  passed  the 
dead-point ;  but  the  further  the  piston  has  travelled 
before  ignition  is  effected,  the  less  the  compression, 


d1 


FIG.  41. 

and  consequently  the  less  the  power  exerted.  Once 
the  engine  is  well  started,  the  momentum  of  the 
fly-wheel  will  carry  the  piston  over  the  dead-point, 
even  if  the  ignition  takes  place  at  the  instant  of 
greatest  compression,  which  is  the  time  of  greatest 
efficiency. 

One  simple  means  of  effecting  the  change  of 
"  timing "  the  spark,  when  a  primary  coil  is  used  to 
effect  ignition,  is  shown  conventionally  at  Fig.  41. 
Let  A  be  a  handle  or  lever,  capable  of  being  set  at 
any  point  by  "  notching  "  or  by  screw  and  nut.  This 
plays  in  any  convenient  portion  of  the  frame  of  the 


98      PRIMARY  AND  SECONDARY  COILS. 

car,  cycle,  or  engine  A'.  The  lower  extremity  of  this 
handle-bar  or  lever  has  a  hinged  rod  extension,  which 
engages  in  a  tooth  c,  which  can  be  run  along  the 
quadrant  of  the  trapezoidal  plunger  D  D.  This  tooth 
is  struck  by  the  half-speed  cam  B,  once  in  each 
revolution,  at  the  same  time  driving  the  trapeze  rod 
backwards  (against  the  pressure  of  the  spring  E)  and 
causing  the  platinum  boss  H,  of  the  plunger  D,  to 
wipe  against  the  platinum  tip  G  of  the  ignition-plug 
F.  Directly  the  spring  returns  the  rod,  a  spark  is 
produced  between  G  and  H,  owing  to  the  "  break " 
which  then  occurs  in  the  circuit  between  the  battery 
J  and  the  coil  K,  at  the  point  G  H.  (The  reader  will 
observe,  for  the  sake  of  clearness,  we  have  placed  the 
half-speed  cam  separate  from  the  engine  and  cylinder; 
whereas,  in  practice,  it  would  form  part  and  parcel 
thereof.)  When  the  tooth  is  in  the  position  depicted 
at  C,  the  firing  would  take  place  before  the  piston  has 
reached  the  end  of  its  inward  stroke,  just  before  the 
full  compression  has  taken  place.  If,  by  lowering 
the  lever  A,  the  tooth  were  set  as  shown  at  c',  firing 
would  occur  at  the  instant  when  the  piston  is  at  the 
point  of  greatest  compression,  while,  if  by  yet  further 
lowering  the  lever  A,  the  tooth  or  lug  were  placed  in 
the  position  indicated  by  the  dotted  figure  at  c",  the 
firing  would  be  retarded  until  the  piston  had  travelled 
somewhat  on  its  outward  stroke,  and  so  on  for  any 
intermediate  positions. 

It  is  advisable  that  the  "live,"  +,  or  positive  wire 
of  the  coil  should  be  connected  to  the  platinum- 
tipped  rod  D,  which  must  be  insulated.  This  is 
effected  by  lining  the  interior  of  the  ignition-plug 
with  porcelain,  and  the  extension  of  the  rod  D,  where 


PRIMARY  AND  SECONDARY  COILS.      99 

it  passes  into  the  guide  E',  should  also  be  insulated. 
The  negative  or  — pole  of  the  battery  J  must  be 
"  earthed,"  that  is  to  say,  connected  to  any  part  of  the 
engine  frame. 

It  will  be  evident,  from  a  moment's  examination  of 
the  figure,  that  this  arrangement  admits  of  consider- 
able variation  to  suit  particular  requirements,  such  as 
firing  the  charge  from  the  outside  of  the  cylinder  (as 
was  formerly  done  in  stationary  engines).  To  effect 
this,  an  insulated  V-shaped  brass  lever  pivoted  at  its 
apex,  and  pushed  on  one  side  by  a  suitable  spring, 
rubs  against  a  springy  wire  or  plate,  both  being 
affixed  over  against  the  hole  in  the  cylinder  where 
the  explosion  is  desired.  When  the  extension  of  the 
trapeze  D  is  pushed  backward  by  the  impact  of  the 
cam  B  striking  the  tooth  C,  it  causes  the  upper  limb  of 
the  lever  to  slide  off  the  wire  or  plate,  thus  breaking 
the  circuit  between  battery  and  coil  at  the  point, 
when  a  spark  is  produced,  and  explosion  of  the 
gaseous  mixture  results. 

As  the  contact  is  a  rubbing  or  "wiping"  one,  the 
surfaces  always  remain  bright  by  friction.  After  con- 
tact has  been  broken,  and  the  cam  B  has  passed  over 
the  tooth  C,  the  counter-spring  pressing  on  the 
V-shaped  lever  reasserts  its  power,  and  slides  the 
lever  on  the  wire  or  against  the  plate,  again  making 
contact.  Connection  must  be  made  between  the 
negative  end  of  the  battery  and  engine  on  the  one 
hand,  and  between  the  positive  end  of  coil  and 
V-piece  on  the  other. 

Since  the  advent  of  the  "dynamo  coil"  and  of  the 
"  magneto,"  in  which  the  timing  of  the  ignition  has 
been  rendered  both  simple  and  certain,  ignition  by 


ioo    PRIMARY  AND  SECONDARY  COILS. 

primary  coil,  except  only  for  gas-burner  lighting,  has 
become  almost  entirely  obsolete,  and  we  have  men- 
tioned it  here  mainly  for  the  sake  of  historical 
sequence.  There  is,  however,  one  notable  exception 
as  regards  primary  coils,  and  that  is  to  be  found  in 
the  sparking  plug  recently  patented  by  Major  J.  A. 
Torrens,  and  which,  in  view  of  its  simplicity,  its  sus- 
ceptibility of  being  easily  and  accurately  timed, 
promises  to  be  largely  employed — and  which  we  will 
therefore  describe  somewhat  in  detail. 

The  following  is  a  condensation  of  the  principle  of 
Major  Torrens'  specification : 

The  improved  apparatus  consists  of  a  single 
primary  coil,  having  two  breaks  in  the  circuit,  one  of 
which  is  normally  open,  and  is  closed  by  any  suitable 
mechanical  means  when  the  engine  is  working,  such 
as  by  a  cam  of  the  two-to-one  gear ;  while  the  other 
is  normally  closed,  and  is  opened  by  the  establish- 
ment of  a  current  in  the  inductance  coil,  when  the 
first  gap  or  break  is  closed  somewhat  in  the  same 
manner  that  an  ordinary  contact-breaker  has  its 
hammer  attracted  by  the  iron  core  when  the  battery 
current  is  allowed  to  flow,  thus  breaking  the  contact 
immediately  on  the  passage  of  the  energising  current 
The  spark  produced  at  the  second  gap  which  is 
arranged  to  be  placed  in  the  combustion  chamber,  or 
at  any  rate  in  contact  with  a  portion  of  the  explosive 
charge,  depends  upon  what  is  commonly  called  the 
"  extra  current "  in  the  primary  induction  coil  circuit. 
(The  reader  will  remember  that  this  device  is 
specially  intended  to  make  use  of  a  primary  coil 
only,  therefore  doing  away  with  all  the  incon- 
veniences due  to  the  employment  of  the  high-tension 


PRIMARY  AND  .SECQNM&Y- C01LS'  101 

currents  inherent  to  this  system.)     The  spark  is  pro- 
portional to  the  rate  of  change  of  magnetic  flux  due 
to  the  current  in  that  coil.     Consequently  the  quicker 
the  breaking  of  the  circuit  at  the  sparking  electrodes 
can  be  effected  the  greater  will  be  the  "  extra  current." 
To  effect  a  sudden  break  one  of  the  sparking  elec- 
trodes (which  is  movable)  is  quickly  retracted  from 
contact  with  the  other  by  a  blow  from  an  iron  plunger 
which  forms  the  core  of  the  primary  coil,  which,  in 
obedience  to  the  laws  that  govern  the  action  of  the 
solenoid,  is  instantly  sucked  up  towards  the  centre  of 
the  primary  coil    on  the  advent  of  the  energising 
current.     Farther,  since  the  rate  of  change  of  mag- 
netic flux  will  not  be  at  a  maximum  if  the  circuit  be 
broken  before  the  said  current  has  reached  its  steady 
value,  the  distance  between  this  movable  core  and 
the  movable  electrode  is  spaced  so  as  to  allow  the 
energising  current  time  to  have  reached  its  full  value 
before  the  blow  is  delivered.     The  movable  electrode 
is  returned  to  its  normal  position  in  contact  with  the 
fixed  electrode  by  its  own  weight,  or  preferably  by 
means  of  a  spring,  and  is  relieved  of  any  weight  or 
impact  due   to  the   return  of  the  magnetic  core  by 
providing    a   rest   or   stop    for   the   latter,   which    is 
secured   to  a   fixed   part  of  the  plug.     The  interior 
space  in  which  the  movable  electrode  and  magnetic 
core  slide,  and  which  is  in  communication  with  the 
interior  of  the  cylinder,  is  made  gas-tight,  and  the 
sliding   magnetic   core  which    preferably  fills   up    as 
much  as  possible  of  the  space  which  is  not  occupied 
by  the  movable  electrode  is  fluted  longitudinally,  of 
otherwise  formed   to  allow  the  free  passage  of  ail 
during  its  movement. 


102     PRIMARY  AND  SECONDARY  COILS. 


FIG.  42. 
MAJOR  TORREN'S  PATENT  "PRIMARY  COIL"  SPARKING  PLUG 


PRIMARY  AND  SECONDARY  COILS.    103 

In  Fig.  42  we  have  a  longitudinal  section  of  this 
"  primary  coil "  sparking  plug.  As  shown  here,  a 
hollow,  fluted,  iron  or  steel  sliding  core  or  hammer,  a, 
surrounds  a  rod,  b,  of  non-magnetic  metal,  which 
constitutes  the  movable  sparking  electrode,  which  is 
tipped  with  platinum  in  the  usual  manner.  The 
electrode,  b,  is  urged  into  contact  with  e  by  means  of 
a  light  spring,  f,  while  the  core,  a,  normally  rests  on 
the  ledge  of  a  stirrup,  d,  which  is  screwed  into  the 
threaded  plug,  g,  and  which  carries  the  fixed  elec- 
trode, the  face  of  which  is  also  platinum-tipped.  The 
electrode,  b,  is  formed  with  a  collar,  c,  between  which 
and  the  near  end  of  the  core,  a,  is  a  certain  clearance 
or  space,  the  amount  of  which  is  determined  by  the 
electrical  and  magnetic  constants  of  the  inductance 
coil.  The  parts  a  and  b  are  enclosed  within  a  non- 
magnetic metal  tube,  t,  occupying  the  core  of  the 
solenoid  bobbin,  jt  and  closed  at  its  upper  end  by  a 
plug,  k,  of  brass,  or  of  other  non-magnetic  metal, 
which  is  cored  to  serve  as  a  guide  for  the  electrode, 
b,  and  also,  forms  an  abutment  for  the  spring,  f. 
The  bobbin,  /,  and  the  tube,  /,  are  insulated  from 
the  plug,  gy  by  the  insulating  packing,  /,  and  an  ex- 
ternally screw-threaded  insulating  ferrule,  m,  on 
which  the  metal  plug,  g,  is  screwed. 

The  electric  circuit  is  completed  from  a  suitable 
battery,  accumulator,  or  low-tension  magneto,  through 
the  coil,  ht  bobbin,  /,  tube,  z,  plug,  k,  spring,  /,  elec- 
trodes, b  and  <?,  and  stirrup,  </,  to  the  metal  plug,  gt 
which  is  screwed  into  the  engine  castings. 

We  can  now  pass  to  the  consideration  of  the 
"  secondary  "  coil,  which  is  the  one  usually  employed 
for  the  petrol-engine  ignition,  as  it  lends  itself  readily 


io4    PRIMARY  AND  SECONDARY  COILS. 

to  the  solution  of  the  problem  of  producing  the  spark 
at  any  part  of  the  circuit,  independently  of  the  point 
at  which  the  battery  contact  is  broken. 

As  the  satisfactory  working  of  petrol  motors  is 
largely  dependent  on  the  efficiency  of  the  coil,  we  shall 
enter  rather  fully  into  the  principles  which  govern  its 
action,  and  follow  on  by  giving  such  constructional 
details  as  will  enable  the  reader  to  make  a  serviceable 
coil  if  desired,  or  to  localise  the  faults  and  repair  the 
same  in  a  coil  which  may  not  be  doing  its  proper 
work. 

The  "secondary,"  "sparking,"  or  "Ruhmkorff" 
coil  consists  in  six  essential  portions— ;viz.,  (a)  the 
iron  bundle  or  core,  (b)  the  primary  winding,  (c)  the 
secondary  winding,  (d)  the  contact  breaker,  (e)  the 
condenser,  (/)  the  insulation,  (s)  screw  tip,  (P)  con- 
nections. 

At  Fig.  43  we  give  an  illustration  of  a  typical  coil 
in  which  all  these  parts  are  shown.  As  in  the  various 
makes  of  coils  these  parts  may  be  modified  in  form 
or  in  position,  we  have  lettered  these  portions,  and 
shall  make  use  of  the  same  lettering  in  the  following 
illustrations  to  indicate  the  same  parts,  whatever  may 
be  the  changes  introduced,  either  in  form  or  in  posi- 
tion. 

The  iron  core  a  consists  in  a  cylindrical  bundle  of 
annealed  soft  iron  wire,  the  diameter  of  the  core  being 
usually  about  \  of  its  total  length.  It  is  essential  to 
the  good  working  of  a  coil  that  the  iron  should  be 
exceedingly  soft,  so  that  it  may  quickly  and  fully  take 
up  the  lines  of  force  arising  from  the  passage  of  an 
electric  current,  and  as  quickly  return  to  its  normal 
condition  when  the  flow  ceases.  For  this  reason  it  is 


PRIMARY  AND  SECONDARY  COILS.     105 




r2n;~i  Mi 


1 


io6    PRIMARY  AND  SECONDARY  COILS. 

usual  to  "  anneal "  the  bundle  of  soft  iron  wires  con- 
stituting the  core  by  bringing  it  to  a  bright  red  heat 
in  a  clear  fire  and  allowing  it  to  cool  very  gradually 
afterwards.  The  function  of  the  core  is  to  concentrate 
the  lines  of  magnetic  force  set  up  by  the  primary 
current  in  its  flow  round  the  coils  of  the  primary  wire 
b,  as  closely  as  possible  to  the  space  occupied  by  the 
coils  of  the  secondary  winding  c.  In  all  those  cases 
in  which  a  "  trembling "  contact-breaker,  d  d't  is 
attached  to  the  coil,  it  also  serves  to  make  and  break 
rapidly  the  contact  between  the  battery  (or  other 
source  of  current)  and  the  coils  of  the  primary,  which 
it  does  automatically,  by  acquiring  magnetism,  and 
attracting  the  iron  bob  d'  when  the  current  is  on. 
(during  the  contact  of  the  spring  against  the  platinum- 
tipped  screw  d\  and  as  suddenly  allowing  it  to  fly 
back,  and  thus  re-establish  the  contact,  when  the 
contact  has  thus  been  broken. 

When  the  two  ends  of  the  primary  P  P  are  con- 
nected to  a  battery  or  accumulator,  the  current  flows 
along  through  the  contact  screw  d  to  the  contact 
spring  supporting  the  bob  or  hammer  d'  round  the 
coils  of  the  primary  b  b  b  b.  In  so  doing  the  current 
magnetises  the  core  a,  attracts  the  hammer  d',  and 
breaks  contact  between  the  spring  and  the  screw 
on  the  pillar  d.  This  causes  the  core  to  lose  its 
magnetism,  which,  ceasing  to  pull  the  hammer  d't 
allows  the  spring  to  reassert  its  power,  bringing  it 
again  in  contact  with  the  screw  tip  s,  when  the  same 
series  of  movements  recur,  and  continues  as  long 
as  current  is  supplied  by  the  battery,  and,  as  we 
have  explained,  the  result  of  this  making  and 
breaking  contact  between  the  primary  coil  and  the 


PRIMARY  AND  SECONDARY  COILS.    107 

battery  is  to  set  up  transient  currents  in  the  primary 
wire. 

Surrounding  the  primary  wire  coils  b,  but  carefully 
separated  from  them  by  the  insulating  material  ft  is 
the  secondary  wiring,  consisting  of  several  thousands 
of  turns  of  fine  wire,  c  c.  These  are  not  connected 
in  any  way  to  the  primary  coils  b  b — nevertheless  by 
influence,  at  the  instant  that  contact  is  made  and 
broken  on  the  primary  circuit,  currents  are  induced 
in  the  coils  of  the  secondary  ;  and  these  currents  are 
higher  in  tension  and  smaller  in  quantity  than  those 
flowing  through  the  primary  coils,  in  the  same  ratio 
that  the  windings  of  the  secondary  exceed  the  wind- 
ings of  the  primary. 

We  have  also  noticed  that  the  current  self-induced 
in  the  primary  wire  b,  being  opposed  to  the  battery 
current,  sets  up  a  counteracting  effect.  The  end 
served  by  the  condenser  e  is  to  take  up  and  store  this 
self-induced  current  until  the  next  contact  takes  place, 
so  as  to  minimise  the  lowering  of  magnetisation,  which 
would  otherwise  take  place  in  the  iron  core  at  these 
instants.  By  this  means,  the  pressure  or  E.M.F.  set 
up  in  the  secondary  wire  is  greatly  exalted  when  the 
"  breaks  "  take  place,  so  much  so,  that  a  coil  that  will 
barely  give  TV~in-  spark  without  a  condenser  will 
easily  furnish  an  inch  spark  if  fitted  with  a  suitable 
one.  The  condenser  consists  virtually  of  two  sheets  of 
tinfoil  separated  from  each  other  by  some  insulating 
material,  usually  paraffined  paper.  In  order  that  it 
may  take  up  the  self-induced  current  set  up  in  the 
primary,  these  two  sheets  of  tinfoil  are  connected 
respectively — one  to  the  beginning  of  the  primary 
wire  by  where  it  joins  the  spring  of  the  contact-breaker 


io8    PRIMARY  AND  SECONDARY  COILS. 

d',  and  the  other  to  the  pillar  carrying  the  screw  of 
the  contact  breaker  d.  In  order  to  save  space  it  is 
usual  to  cut  the  tinfoil  sheets  into  many  squares,  and 
to  form  two  separate  booklets  by  joining  two  sets  of 
half  the  number  of  sheets  along  one  edge,  to  lap  the 
pages  of  one  book  into  the  pages  of  the  other,  separat- 
ing each  page  with  a  sheet  of  paraffined  paper.  The 
last  essential  we  have  to  consider  is  the  insulation// 
This  is  perhaps  the  most  important  of  all.  When 
it  is  remembered  that  to  produce  a  -J-in.  spark 
in  air,  a  pressure  of  25,000  volts  is  needed,  it  will 
be  abundantly  evident  that  to  withstand  the  pres- 
sures set  up  in  j-in.  or  i-in.  spark  coils,  the  insu- 
lating material  must  be  of  the  very  best,  and  must 
be  used  in  such  a  way  as  to  insure  the  highest 
insulation  at  those  points  wherein  the  tendency  to 
leakage  is  great. 

Tape  dressed  with  shellac  varnish  is  the  insulation 
usually  employed  between  the  iron  core  and  the 
primary  wire.  The  primary  wire  itself  may  be  either 
cotton  or  silk  covered  ;  in  either  case  it  should  be  well 
basted  with  melted  paraffin  wax.  This  excellent  in- 
sulator is  also  used  to  saturate  the  paper  separating 
each  layer  of  secondary  wire,  and  also  to  seal  up  the 
heads  of  the  coil.  Paraffin  wax,  when  employed  for 
insulating  purposes,  should  be  preliminarily  melted 
up  with  some  dry  powdered  chalk,  allowed  to  settle 
while  still  fluid,  and  poured  off  from  the  dregs.  This 
treatment  removes  any  acid  which  might  be  present 
in  the  commercial  article.  As  paraffin  when  at  all 
burnt  is  not  nearly  so  good  an  insulator  as  when  in  its 
normal  state,  the  greatest  care  must  be  taken  not  to 
overheat  it.  For  this  reason  it  is  advisable  to  melt 


PRIMARY  AND   SECONDARY  COILS.     109 

it,  and  keep  it  melted,  h  bain  Marie,  or  in  a  water- 
jacketed  vessel. 

The  insulation  between  the  primary  and  secondary 
windings  should  be  ebonite,  either  in  the  shape  of  a 
thin,  cylindrical,  hollow  tube,  made  all  in  one  piece, 
and  which  fits  tightly  over  the  wound  primary,  or  else 
as  a  tube,  made  by  rolling  thin  ebonite  sheet  (about 
•fa  in.  thick)  tightly  round  the  primary,  and  fastening 
down  the  edge  with  Prout's  elastic  glue,  applied  with 
an  iron  sufficiently  hot  to  melt  it.  Seven  turns  of 
sheet  of  the  afore-mentioned  thickness  will  give  suffi- 
cient insulation.  This  tube  should  extend  quite  to 
the  end  of  the  core,  in  those  coils  in  which  a  contact- 
breaker  is  employed  on  the  coil,  and  should  project 
\  in.  at  each  end  beyond  the  core  in  those  in  which 
the  contact  is  broken  by  mechanical  means,  indepen- 
dent of  the  coil.  The  "  heads  "  of  the  coil,  to  which 
the  outer  connection,  or  "  terminals,"  are  affixed, 
should  also  be  of  ebonite,  as  also  the  outer  case  or 
jacket. 

Although  it  is  possible  to  wind  a  serviceable  coil 
with  bare  copper  wire  for  the  secondary,  depending 
only  on  the  intervening  air  as  the  insulation,  yet  as 
this  requires  a  special  "spacing"  winder,  to  insure 
each  succeeding  turn  of  wire  lying  at  a  determinate 
distance  from  its  neighbour,  we  shall  not  make  any 
further  mention  of  this  except  to  advise  our  readers 
who  may  by  chance  have  to  repair  a  coil  wound  with 
bare  wire,  to  discard  this,  and  rewind  with  silk-covered 
wire  of  the  same  gauge.  We  therefore  recommend 
silk  covering  as  the  insulation  of  the  secondary,  sup- 
plemented with  copious  basting  with  melted  paraffin 
wax. 


no     PRIMARY  AND  SECONDARY  COILS. 

We  summarise  the  contents  of  this  section  by 
saying  that  when  a  current  is  interrupted  in  its  passage 
along  a  coil  of  primary  wire  surrounded  by  a  coil  of 
secondary  wire,  an  induced  current  is  set  up  in  the 
coils  of  this  secondary  wire,  and  can  be  drawn  off  from 
its  extremities  ;  that  this  current  is  transient  and 
manifests  itself  at  the  instant  of  making  and  breaking 
contact  only  at  the  primary  ;  that  the  pressure  of  the 
current  thus  set  up  bears  the  same  relation  to  that  of 
the  original  current,  as  do  the  number  of  turns  of  wire 
contained  in  the  secondary  to  those  contained  in  the 
primary.  Also  that,  to  minimise  the  "  backlash  "  effect 
of  the  self-induction  in  the  primary  itself  it  is  neces- 
sary to  use  a  condenser  ;  and,  lastly,  that  the  most 
perfect  insulation  of  the  secondary  is  absolutely 
essential  to  the  production  of  a  good  long  spark.  We 
can  now  turn  to  the  constructional  details. 

We  will  take  as  our  first  example  a  coil  capable  of 
of  giving  sparks  of  about  I  in.  long  in  air,  since  by 
varying  the  quantities  of  the  wires  used,  and  the 
general  dimensions  of  the  parts  in  proportion  to  the 
length  of  spark  required,  coils  capable  of  giving  J-in. 
or  f -in.  sparks  can  be  constructed. 

We  will  begin  by  describing  a  coil  fitted  with 
"  trembler  " — that  is  to  say,  a  contact-breaker  actuated 
by  the  iron  core  itself,  and  then  point  out  the  modi- 
fications required  in  connections,  etc.,  where  it  is 
intended  that  the  contact  should  be  made  and  broken 
by  mechanical  means  only. 

The  core  should  consist  in  a  bundle  of  perfectly 
straight  soft  iron  wires,  7  ins.  long,  sufficient  in  num- 
ber to  make  a  solid  cylinder  f  in.  in  diameter.  To 
make  this  -a  couple  of  brass  curtain-rings  f  in.  inside 


PRIMARY  AND  SECONDARY  COILS,    in 

diameter  should  be  procured,  the  iron  wires  placed  in 
these  while  being  held  at  about  6  ins.  apart.  When 
the  rings  are  nearly  full,  additional  wires  should  be 
cautiously  pushed  in  at  the  centre  of  the  extremities 
until  no  more  can  be  inserted,  and  the  rings  fit  quite 
tightly.  Under  this  treatment  the  middle  of  the 
bundle  may  bulge  a  little.  This  can  be  remedied  by 
binding  tightly  a  turn  or  two  of  the  same  soft  iron 
wire  round  the  centre,  and  twisting  the  ends  of  this 
binding  wire  together.  Care  must  be  taken  that  the 
two  ends  of  the  bundle  are  perfectly  level.  If  not  so, 
they  must  be  bound  round,  and  filed  until  they  are. 
The  iron  core  should  now  be  placed  in  a  clear  fire, 
until  it  gets  red-hot  ;  then  the  fire  allowed  to  die 
down,  go  out,  and  get  quite  cold.  This  insures  the 
thorough  annealing  of  the  iron  bundle,  a  point  of  the 
highest  importance. 

The  next  operation  is  to  bind  this  core  tightly 
round  with  tape.  Having  pushed  one  of  the  rings 
down  on  the  core  for  about  an  inch,  from  one  ex- 
tremity, one  turn  of  tape,  about  Jin.  wide,  is  to  be 
bound  round  the  bared  end,  pulling  as  tightly  as 
possible,  continuing  the  winding  spirally  downwards 
towards  the  ring.  An  assistant  will  now  push  the 
ring  further  down,  and  remove  any  iron  wire  binders 
that  may  have  been  used,  the  tape  winding  being 
continued  spirally  towards  the  other  end,  as  tightly 
as  possible,  until  both  rings  have  been  drawn  off,  and 
the  tape  bound  round  from  end  to  end.  The  ter- 
mination of  the  tape  is  now  stitched  down  to  the 
layer  below,  and  cut  off  flush  with  the  core. 

To  prevent  the  core  rusting,  and  to  insure  good 
insulation  between  the  iron  of  the  core  and  the 


n2    PRIMARY  AND  SECONDARY  COILS. 

primary,  it  is  desirable  to  soak  the  completed  and 
taped  core  in  melted  paraffin  wax  until  no  more 
bubbles  make  their  appearance.  It  should  then  be 
reared  on  end  to  drain  and  set. 

The  next  operation  is  to  wind  this  core  with  two 
layers  (about  J  Ib.)  No.  1 8  d.c.c.  wire.  Finer  wire  may 
be  used,  such  as  No.  20  ;  but  owing  to  the  "choking" 
effect  produced  by  the  high  self-induction  of  the  finer 
wire,  this  necessitates  the  use  of  more  accumulator 
cells  to  get  the  same  current.  If  coarser  wire  were  to 
be  used,  too  much  current  would  flow,  and  the  accu- 
mulator would  "  run  down  "  too  quickly. 

The  core  may  be  wound  with  this  primary  wire 
either  entirely  by  hand,  or  better,  by  driving  a  French 
nail  some  distance  in  the  centre  of  the  iron  bundle  at 
one  end  and  a  flattened  iron  wire  at  the  other,  then 
supporting  the  core  by  these  two  projections  between 
the  slits  made  at  the  top  of  two  standards  erected  on 
a  baseboard.  The  wire  end  should  be  bent  into  the 
shape  of  a  crank  or  handle,  so  that  a  rotary  motion 
may  be  easily  imparted  to  the  core.  Fastening  down 
one  end  of  the  No.  18  wire  by  tying,  at  about  Jin. 
from  the  extremity  of  the  core  (leaving  about  3  ins. 
free  for  after-connection),  the  operator  winds  on 
tightly,  evenly,  and  closely,  one  layer  of  the  said  wire, 
until  he  reaches  to  within  \  in.  of  the  other  extremity 
of  the  core,  when,  winding  always  in  the  same  direc- 
tion, he  winds  on  a  second  layer,  riding  over  the  first, 
and  when  he  arrives  at  the  starting  extremity  he  ties 
the  end  firmly  down  and  cuts  off  the  wire,  leaving  as 
before  a  free  piece,  3  ins.  in  length.  The  wound  core 
is  again  treated  as  before  with  a  bath  of  melted 
paraffin  wax,  then  reared  on  end  to  drain  and  set. 


PRIMARY  AND  SECONDARY  COILS.     113 

We  now  turn  our  attention  to  the  insulation 
between  the  primary  and  the  secondary.  This  is  of 
the  highest  importance,  and  a  little  care  expended  on 
this  part  will  be  well  repaid  by  the  greatly  superior 
results  in  point  of  spark  length,  and  by  the  durability 
of  the  coil  when  once  made. 

If  possible,  an  ebonite  tube  of  sufficient  inside 
diameter  to  allow  the  wound  core  to  be  slid  into  it 
with  a  fair  fit  should  be  chosen.  This  should  have 
a  wall  thickness  or  "  shell,"  from  -fa  in.  to  £  in.  The 
length  should  be  that  of  the  iron  core.  If  the  coil 
is  to  be  of  the  square  pattern,  with  trembler,  and 
fitted  with  heads,  the  two  ends  of  the  tube  should 
have  screw-threads  cut  in  them  for  a  length  of 
about  §  in.,  on  which  the  heads  can  afterwards  be 
screwed. 

If  circumstances  prevent  the  operator  from  pro- 
curing a  solid  tube,  a  very  good  substitute  can  be 
made  by  taking  a  strip  of  very  thin  sheet  ebonite 
(about  --ff  in.  thick)  as  wide  as  the  core,  and  of  suffi- 
cient length  to  make  about  seven  turns  round  the 
core.  A  wooden  mandrel  or  form,  about  J  in.  less  in 
diameter  than  the  wound  core,  and  an  inch  or  two 
longer,  is  now  procured.  The  sheet  of  ebonite  is 
placed  in  a  vessel  of  boiling  water.  This  will  soften 
it  sufficiently  to  enable  it  to  be  rolled  tightly  round 
the  wooden  cylinder,  so  as  to  form  a  tube,  which 
must  be  tied  down  tightly  with  wide  tape,  laid  on 
spirally.  When  the  tube  is  quite  cold  and  hard  the 
tape  will  be  removed,  when  it  will  be  found  that  the 
ebonite  will  retain  its  shape — viz ,  of  a  tube  rather 
less  in  diameter  than  the  wound  core. 

This  tube  must  be  allowed  to  dry  thoroughly  from 


H4     PRIMARY  AND   SECONDARY  COILS. 

any  adherent  moisture,  and  then  coaxed  over  the 
wound  core,  which  it  will  embrace  firmly  by  reason  of 
its  springiness.  The  extreme  outside  lap  of  the 
ebonite  forming  this  tube  should  be  lifted  slightly, 
and  a  brush,  charged  with  a  thick  solution  of  shellac 
dissolved  in  methylated  spirits,  run  along  the  edge  for 
a  depth  of  about  J  in.  The  lap  should  then  be 
allowed  to  fall  back  in  its  place,  and  pressed  well 
down.  After  this  the  tube  should  again  be  tightly 
bound  round  with  tape  and  set  aside  to  dry.  By  this 
means  a  well-fitting  insulating  tube  is  obtained.  A 
built-up  tube  of  this  type  is  quite  equal  to  a  solid 
tube  as  regards  its  insulating  powers,  etc. — and  for 
coils  to  which  it  is  not  necessary  to  screw  on  heads, 
quite  as  convenient ;  but  of  course  it  would  be  im- 
practicable to  cut  a  thread  on  such  a  tube,  so  that  in 
using  a  built-up  tube  it  will  be  necessary,  if  heads  are 
to  be  fitted,  to  put  plain  holes  through  these  latter, 
and  cement  them  on  with  hot  melted  shellac  or  good 
sealing-wax. 

The  tube  having  been  fitted  and  the  tape  removed, 
the  winding  of  the  secondary  constitutes  the  next 
step.  For  this  purpose  a  winder  must  be  constructed. 
On  a  board  9  ins.  long,  6  ins.  wide,  and  I  in.  thick,  are 
erected  two  standards,  one  at  each  end  centrally. 
These  standards  should  be  Sins,  high,  i^  ins.  wide, 
and  |  in.  thick.  Through  the  centres  of  the  lower 
ends  of  these  standards,  at  about  2  ins.  from  the  base 
and  exactly  facing  one  another,  i-in.  holes  should  be 
drilled  to  admit  of  the  passage  of  a  £-in.  steel  rod, 
which  serves  to  go  through  a  central  hole  of  the 
bobbin  containing  the  silk-covered  wire  with  which 
the  secondary  is  wound. 


PRIMARY  AND   SECONDARY  COILS.     115 

At  a  height  of  about  4^  ins.  from  this  first  pair  of 
holes  a  second  pair  is  drilled  in  the  standards,  also 
exactly  opposite  one  another,  and  a  slit  ^  in.  wide 
cut  down  to  reach  these  holes  from  the  top  ends  of 
the  standards.  These  serve  to  support  a  second  rod, 
which,  in  its  turn,  carries  the  core,  etc.,  on  which  the 
secondary  wire  is  to  be  wound.  But  this  second  rod 
is  not  all  in  one  piece.  On  the  one  side  it  consists  in 
an  i-in.  hard  iron  round  rod,  about  4-|ins.  long,  nicely 
pointed  at  one  end,  whicji  can  be  pushed  in  the  centre 
of  the  iron  core  between  the  iron  wires,  and  at  the 
other  end,  of  a  rod  made  of  No.  16  soft-iron  wire 
about  I  ft.  long,  doubled  at  its  middle,  and  twisted 
together  nearly  up  to  the  end,  so  as  to  form  a  kind  of 
two-tined  fork  at  that  extremity,  where  the  "  tines  " 
must  be  bent  forward  parallel  to  each  other,  at  a 
distance  of  about  \  in.  apart.  At  about  the  middle 
the  twisted  rod  is  bent  twice  at  right  angles,  so  as  to 
form  a  crank  or  handle.  The  prongs  of  the  fork 
having  been  pushed  in  between  the  iron  wires  of  the 
wound  primary,  at  the  opposite  end  to  which  the 
pointed  rod  was  forced  in,  the  primary,  with  its 
ebonite  insulation  on,  is  slung  between  the  slits  in  the 
standards,  and  is  ready  for  winding  by  turning  the 
cranked  handle. 

The  wire  to  be  used  for  winding  the  secondary  is 
No.  36  silk-covered  copper.  If  good  single-covered 
-an  be  procured,  free  from  unevenness,  and  par- 
ticularly from  bare  places,  it  is  to  be  preferred  to 
double-covered,  as  it  lies  closer,  and  hence  nearer  to 
the  intense  inducing  field ;  but  if  the  covering  be 
faulty  it  will  be  better  to  have  recourse  to  double- 
covered  wire.  The  quantity  of  wire  required  will  be 


n5    PRIMARY  AND   SECONDARY  COILS. 

about  J  Ib.  for  a  ^-in.  spark  coil,  or  about  I  Ib.  if  the 
coil  is  intended  to  give  i-in.  spark. 

Before  proceeding  with  the  actual  winding  it  will 
be  needful  to  prepare  sufficient  paraffined  paper  to 
place  between  each  layer  of  wire  in  order  to  insulate 
the  succeeding  layers  the  one  from  the  other.  As 
we  shall  require  paraffined  paper  for  the  condenser 
also,  it  will  be  advisable  to  make  the  whole  at  one 
operation. 

To  prepare  paraffined  paper  some  twelve  or  four- 
teen sheets  of  good  white  demy  paper,  free  from 
specks  and  holes,  must  be  chosen  by  examination 
between  a  strong  light  and  the  eye,  all  defective 
sheets  being  rejected.  The  size  should  be  about 
22  ins.  by  iSins.  About  thirty-nine  strips  pins,  long 
by  6  ins.  wide  will  be  required  for  insulating  the 
secondary,  and  about  sixty  squares  5  ins.  long  by  6  ins. 
for  the  condenser.  By  laying  the  sheets  of  paper 
evenly  and  squarely  one  over  the  other  on  a  flat 
board,  these  two  sizes  may  be  cut  out  with  the  aid  of 
a  straight  metal  rule  and  sharp  knife  at  one  opera- 
tion for  each  size.  A  tin  dish  (a  large  baking  dish 
will  do  nicely)  rather  larger  than  the  sheets  should 
now  be  selected,  and  in  this  should  be  placed  suffi- 
cient paraffin  wax  (previously  rendered  neutral  by 
chalk — see  page  108)  to  cover  the  bottom  to  a  depth 
of  ^in.  when  melted.  The  dish  should  then  be 
cautiously  heated,  preferably  a  bain  Marie,  until  the 
wax  is  all  fused.  The  paper  should  then  be  intro- 
duced sheet  by  sheet,  and,  when  thoroughly  per- 
meated, withdrawn  a  sheet  at  a  time,  care  being 
taken  to  remove  all  superfluity  of  wax  by  drawing 
the  paper  over  the  edge  of  the  tin,  and  allowing  it  to 


PRIMARY  AND   SECONDARY  COILS.     117 

drain  by  one  corner  into  the  dish,  which  must  be  kept 
at  one  steady  temperature  (about  150°  Fahr.)  during 
the  whole  of  the  operation.  After  draining,  each 
sheet  should  be  hung  up  by  one  corner,  with  a  pin 
bent  into  an  S,  on  a  line  to  set  hard.  If  any  sheets 
are  unduly  thick  at  places,  or  show  blobs  of  con- 
gealed wax,  these  should  be  placed  between  sheets  of 
thick  white  blotting-paper,  and  run  over  with  a  fairly 
hot  iron. 

The  bobbin  of  No.  36  silk-covered  wire  is  now 
placed  between  the  standards  of  the  winder,  and  sup- 
ported by  running  the  lower  rod  through  the  central 
hole  in  the  bobbin.  The  beginning  of  the  wire  is  now 
found  and  unrolled.  Three  or  four  inches  of  this  is 
coiled  into  a  tight  helix  round  a  small  pencil,  which 
is  then  withdrawn,  leaving  only  a  helix  of  wire.  This 
is  taken  up  to  the  primary,  which  has  been  previously 
slung  between  standards,  as  directed  above,  and  the 
wire  tied  to  the  ebonite  tube,  say,  at  the  left-hand 
extremity,  at  about  Jin.  from  the  end,  leaving  the 
helix  free  for  future  connection  to  terminals. 

Now  by  turning  the  handle  the  wire  can  be  wound 
off  the  lower  bobbin  and  caused  to  coil  round  the 
ebonite  tube.  Before  commencing  to  wind,  it  will  be 
necessary  to  put  a  turn  or  two  of  paraffined  paper 
tightly  round  the  ebonite  tube,  so  as  to  get  a  perfectly 
smooth  surface  to  wind  on.  When  the  edge  of  this 
paper  has  been  pulled  very  tightly,  it  can  be  made  to 
adhere  to  the  paper  below  by  gently  warming  along 
the  edge  with  a  hot  iron,  which  will  mek  the  wax  and 
cause  it  to  adhere.  The  handle  can  now  be  turned 
and  the  wire  wound  on,  the  greatest  care  being  taken 
to  lay  it  on  smoothly,  closely,  and  without  either  gaps 


n8    PRIMARY  AND   SECONDARY  COILS. 

between  coil  and  coil  or  any  coil  overriding  the  other. 
Kinks  must  also  -be  avoided,  as  they  are  detrimental. 
Should  any  bare  place  show  itself  in  the  wire,  this 
must  be  wrapped  round  with  fine  silk.  Should  a 
break  occur,  the  broken  extremities  must  be  bared  of 
covering,  cleaned  till  quite  bright,  with  a  bit  of  finest 
emery  paper,  twisted  together,  soldered  by  the  aid  of 
a  stout,  hot  copper  rod  and  soft  solder,  using  a  little 
rosin  as  a  flux.  No  soldering  fluid  may  be  used,  as 
this  would  certainly  cause  the  wire  to  rot  and  break. 
When  the  repair  has  been  neatly  executed,  the  joined 
portion  should  be  carefully  bound  round  with  some 
fine  floss-silk  to  insure  insulation.  The  winding  must 
be  continued  until  the  operator  reaches  to  within  ^  in. 
of  the  right-hand  end  of  the  tube,  when  he  will  stop, 
and,  fastening  the  wire  so  that  it  should  not  uncoil,  he 
will  cover  the  layer  of  wire  just  laid  on  with  a  turn 
and  a  half  of  paraffined  paper,  taking  care  that  the 
end  of  the  wire  running  off  the  bobbin  lies  under  the 
lap  of  the  paper  when  this  passes  over  it.  The  paper 
must  be  pulled  very  tightly  and  smoothly,  so  as  to  be 
perfectly  cylindrical  and  without  any  creases,  and 
then  fastened  down,  as  was  the  first  paper.  Again 
turning  the  handle  (always  in  the  same  direction), 
the  operator  winds  on  a  second  layer  of  wire  until  he 
reaches  the  left-hand  extremity,  stopping,  however, 
about  two  turns- short  of  where  he  started.  This  is 
to  cause  the  length  of  the  coils  to  diminish  slightly 
as  the  successive  layers  are  wound  on,  with  a  view  to 
preventing  the  upper  layers  sparking  down  and 
short-circuiting  to  the  ones  below.  Using  all  the 
precautions  recommended  above,  the  operator  con- 
tinues winding,  putting  on  the  first  paper,  then  the 


PRIMARY  AND  SECONDARY  COILS.    119 

layer  of  wire,  then  paper,  and  so  on,  until  the  whole  of 
the  pound  of  No.  36  wire  has  been  coiled  on,  with  the 
exception  of  about  6  ins.,  which  must  be  left  free  for 
future  attachment  to  terminal. 

Te  prevent  uncoiling,  two  or  three  turns  of  pa- 
raffined paper  should  be  rolled  tightly  round  the  last 
layer  of  wire,  taking  care  to  bring  the  free  6-in.  end 
of  wire  out  from  between  the  turns  of  paper,  where  it 
can,  like  tlie  starting  end,  be  coiled  into  a  tight  helix. 
Besides  fastening  the  edges  of  the  last  lap  of  paper 
down  by  heating,  it  will  be  well  to  bind  the  whole 
round  with  a  wide  silk  ribbon,  laid  on  spirally,  so  as 
to  reach  from  one  end  to  the  other,  when  it  can  be 
stitched  down  and  any  excess  cut  off. 

The  winding  of  the  secondary  being  thus  completed, 
the  entire  wound  coil  should  be  plunged  bodily  in  a 
vessel  containing  melted  paraffin  wax.  The  tempera- 
ture must  not  be  allowed  to  exceed  150  degrees  Fahr. 
If  the  vessel  be  deep  enough  to  allow  the  paraffin  to 
entirely  cover  the  coil,  so  much  the  better  ;  it  may  be 
left  therein  until  no  more  bubbles  appear.  When  this 
occurs  the  wax  may  be  allowed  to  cool  a  little,  until 
it  is  just  beginning  to  get  pasty,  when  the  coil  should 
be  withdrawn,  and  set  on  end  (over  the  vessel  sup- 
ported by  two  side  sticks)  to  drain  and  set  hard. 
Should  the  vessel  be  shallow,  the  coil  should  be  set 
on  end,  and  the  upper  end  repeatedly  basted  with 
the  hot  paraffin  wax.  The  vessel  may  now  be  re- 
moved from  the  source  of  heat,  allowed  to  cool  as 
before,  the  basting  being  continued  until  the  paraffin 
begins  to  get  pasty,  when  the  coil  can  be  set  up  to 
drain,  as  previously  recommended. 

The  condenser  next  demands  our  careful  attention. 


i2o    PRIMARY  AND  SECONDARY  COILS. 

From  J  Ib.  of  ordinary  tinfoil  we  cut  out  fifty 
rectangular  sheets  6J  ins.  long  by  4  ins,  wide,  and 
having  placed  our  paraffin-paper  sheets  (see  page  1 16), 
the  size  of  which  is  6  ins.  by  5  ins.,  close  at  hand,  we 
lay  three  of  these  squarely  one  over  the  other  on  a 
flat  board.  In  order  that  the  sheets  should  not  shift 
during  the  subsequent  building-up  of  the  condenser, 
it  will  be  well  to  drive  eight  stout  pins,  upright,  into 
the  board  just  round  the  edges  of  the  paper,  two  at 
opposite  sides  of  each  corner. 

We  now  lay  a  tinfoil  sheet  over  the  paraffin  paper 
so  as  to  leave  a  margin  of  about  \  in.  wide  all  round 
the  tinfoil,  except  on  the  left-hand  side,  where  the 
tinfoil  should  extend  beyond  the  edge  of  the  paper  by 
I  in.  Over  this  is  placed  a  second  sheet  of  paraffined 
paper  squarely  between  the  pin-guides,  then  a  second 
sheet  of  tinfoil.  But  this  time  the  overlapping  inch  of 
tinfoil  must  be  to  the  right-hand  side  of  the  operator. 
Now  another  sheet  of  paper  is  placed  over  the  last 
tinfoil,  over  which  is  laid  another  tinfoil,  with  zYj  over- 
lap to  the  left ;  and  so  on,  paper,  tinfoil,  paper,  tinfoil, 
until  the  whole  tally  of  sheets  have  been  laid  on. 

Particular  care  must  be  taken  that  the  sheets  of 
tinfoil  extend  alternately  to  the  left  and  to  the  right 
of  the  covering  papers. 

Three  or  four  sheets  of  paraffined  paper  should  now 
be  laid  over  the  whole,  and  a  rather  warm  iron  (just 
sufficiently  heated  to  soften  the  paraffin  wax  on  the 
paper,  but  not  enough  to  make  it  run)  laid  on  the  top. 
In  order  to  prevent  adhesion  to  the  iron,  it  will  be 
well  to  place  a  sheet  of  blotting-paper,  of  the  same 
size  as  the  paraffined-paper  sheets,  between  the  iron 
and  these  latter,  The  iron  should  be  left  on  until 


PRIMARY  AND  SECONDARY  COILS.    121 

quite  cold.  Removing  the  iron  and  the  guide-pins, 
the  operator  now  passes  a  thin  knife-blade  between  the 
board  and  the  first  paper,  and  thus  lifts  the  condenser 
without  disturbing  the  sheets.  If  the  last  operation 
has  been  nicely  done,  the  sheets  will  adhere  together," 
and  form  a  fairly  solid  block.  If  not,  it  will  be  advis- 
able to  put  a  long  "  binder  "  of  paraffined  paper  round 
the  condenser  about  its  narrower  width,  leaving  its 
tinfoil  ends  projecting  at  the  longer  extremities.  This 
binder  can  be  fastened  down  upon  itself  by  running  a 
little  paraffin  wax  along  its  edge,  with  a  moderately 
warm  iron. 

When  all  is  set  and  cold,  two  straight  pieces  of  No. 
20  copper  wire,  about  6  ins.  long,  are  made  perfectly 
clean,  and  laid  one  on  each  of  the  projecting  ends  of 
the  tinfoil  sheets.  These  are  carefully  smoothed  out, 
and  then  rolled  round  the  wire  in  the  shape  of  a 
cigarette,  with  the  wire  as  a  core,  until  by  rolling  the 
edge  of  the  condenser  is  reached.  The  wires  should 
project  about  2  ins.  beyond  the  rolled  tinfoils.  A 
needle  should  now  be  threaded  with  some  clean  bare 
No.  36  or  38  copper  wire,  and  the  tinfoil  rolls  stitched 
neatly  round  the  wire  cores.  These  latter  serve  for 
making  connections  between  the  coil  wires  and  the 
condenser. 

In  making  the  condenser  the  following  points  re- 
quire particular  attention: — (i)  The  paper  must  be 
free  from  all  pin-holes  or  thin  places.  (2)  It  must  be 
well  and  evenly  coated  with  paraffin  wax,  but  must  not 
have  any  excess  or  "  blobs."  (3)  The  tinfoils  must 
leave  a  margin  of  paper  all  round  except  at  overlap 
extremities.  The  overlaps,  or  "  tabs,"  must  be  alter- 
nately to  the  right  and  the  left  of  the  length  of  the 


122   PRIMARY  AND  SECONDARY  COILS. 

paraffined  sheets.  (4)  Each  sheet  of  paper,  as  it  is 
laid  on,  should  be  pressed  down  firmly  and  squarely 
(if  needful,  aided  by  a  clean  warm  iron),  so  as  to  form 
a  solid  block.  (5)  No  paraffin  should  be  allowed  to 
'flow  between  the  extending  "  tabs  "  of  tinfoil,  other- 
wise good  metallic  contact  cannot  be  made  to  the  coil 
itself.  (6)  Great  care  should  be  exercised  not  to  tear 
the  protruding  tinfoil  extension. 

We  can  now  take  up  the  contact-breaker  or 
"  trembler."  As  our  coil  is  to  be  as  compact  as  pos- 
sible, we  shall  do  away  with  the  stand  or  base  on 
which  ordinary  Ruhmkorff  coils  are  mounted,  and 


FIG.  44. 

let  all  the  adjustments  and  accessories  be  fitted  to 
the  coil-heads,  etc.,  themselves. 

The  contact-breaker,  Fig.  44,  consists  of  two  por- 
tions— the  vibrating  spring,  with  its  hammer  and 
base,  and  a  brass  strap,  which  strides  over  it,  carry- 
ing the  contact-screw  and  lock-nut.  The  former 
should  be  made  of  a  piece  of  steel  (a  clock-spring 
straightened  out  does  very  well)  about  -g^in.  thick, 
f  in.  wide,  and  2  ins.  long.  A  -|-in.  hole  is  drilled  in 
the  centre  of  each  extremity  of  this,  and  a  bare  j^-in. 
hole  in  the  middle  of  the  strip.  It  is  needless  to 
remark  that  the  steel  must  be  softened  by  heat  to 


PRIMARY  AND  SECONDARY  COILS.    123 

admit  of  these  holes  being  drilled,  and  that  the 
finished  spring  must  again  be  tempered  to  a  deep 
blue  and  plunged  in  water.  From  a  piece  of  soft-iron 
rod  is  now  cut  the  hammer,  which  should  be  fin.  in 
diameter,  and  ^  in.  long,  the  two  ends  being  filed 
perfectly  flat  and  parallel.  In  the  centre  of  this  is 
put  a  hole  (not  reaching  quite  through),  which  must 
be  tapped  to  take  a  ^-in.  Whitworth  screw.  The  iron 
is  then  carefully  softened  and  annealed  by  bringing 
to  a  red-heat  and  gradual  cooling.  While  this  is 
going  on  we  put  a  short  piece  of  No.  16  platinum  wire 
through  the  small  hole  in  the  centre  of  the  spring^ 
when  by  gently  hammering  with  a  flat-faced  hammer 
on  a  smooth  steel  anvil  we  rivet  the  platinum  in, 
causing  it  to  spread  somewhat  on  the  upper  surface, 
so  as  to  form  a  stud  or  button,  about  ^  in.  in  diameter. 
This  is  to  form  one  contact.  A  little  square  of  brass 
is  now  filed  up  from  a  piece  of  f-in.  hard  steel,  to 
form  a  base  for  one  end  of  the  spring.  This  should 
be  f  in.  square,  and  have  a  J-in.  hole  put  through  its 
centre,  corresponding  to  the  hole  at  one  extremity  of 
the  spring.  The  annealed  iron  hammer  is  now 
cleaned  and  attached  to  the  spring  by  a  suitable 
short  cheese-headed  screw,  care  being  taken  that  the 
iron  bob  be  placed  on  the  side  of  the  spring  opposite 
to  that  on  which  the  platinum  button  has  been 
splayed  out  widest.  To  fasten  the  contact-breaker 
down  to  the  case  of  the  coil  a  similar  screw  (only 
rather  larger)  is  selected  to  go  through  the  holes  in 
the  spring  and  block.  This  screw  should  be  fitted 
below  with  a  small  square  or  hexagonal  brass  nut,  to 
enable  contact  to  be  made  with  one  of  the  coil 
terminals,  as  described  later  on.  The  brass  strap 


i24    PRIMARY  AND   SECONDARY  COILS. 

may  be  either  a  casting,  or  made  from  J-in.  sheet 
brass,  bent  four  times  at  right  angles,  thus  _j  |_.  It 
should  be  -J  in.  wide,  s^ins.  long  before  bending,  and 
2  ins.  from  end  to  end  when  bent  into  shape.  The 
feet  should  be  ^  in.  long,  the  height  of  the  bridging 
piece  f  in.  clear  from  the  base,  and  the  width  of  the 
opening  f  in.  A  |-in.  hole  is  put  through  the  centre 
of  each  foot  to  admit  the  screws  by  which  the  strap 
is  to  be  attached  to  the  coil.  A  hole  is  also  to  be 
bored  and  tapped  through  the  centre  of  the  bridging 
piece,  to  take  a  |--in.  Whitworth  brass  screw,  with  -f-in. 
milled  head.  This  latter  screw  must  be  fitted  with  a 
|-in.  lock-nut,  also  milled  round  its  edge,  and  a  ^-in. 
hole  drilled  carefully  for  about  %  in.  up  the  centre  of 
the  stem  of  the  screw,  into  which  is  fitted,  by  gentle 
hammering  and  burring,  a  piece  of  No.  16  platinum 
wire,  which  should  project  about  %  in.  beyond  the  tip 
of  the  screw. 

We  can  now  proceed  to  make  the  outer  box  or 
case,  and  fit  the  coil  therein,  making  the  proper  con- 
nections to  condenser,  contact-breaker,  and  terminals. 
The  case  may  be  made  of  any  hard,  well-seasoned 
wood,  such  as  teak,  mahogany,  or  walnut.  If  the  coil 
has  been  nicely  wound  it  will  not  exceed  in  diameter 
2\  ins.,  in  which  case  the  inside  dimensions  of  the  box 
may  be  3^  ins.  square  by  6|  ins.  long.  The  wood  with 
which  it  is  constructed  should  be  fin.  thick  when 
planed  up,  so  that  the  external  dimensions  will  be 
those  of  a  square  upright  box  4^  ins.  in  the  sides,  and 
7j  ins.  high,  including  the  bottom  and  cover,  which 
latter  is  not  to  be  fastened  down  until  the  coil  and 
condenser  have  been  put  in  place.  Should,  however, 
through  careless  winding,  the  diameter  of  the  coil 


PRIMARY  AND  SECONDARY  COILS.    125 

exceed  2\  ins.,  the  width  of  the  sides  of  the  box  must 
be  correspondingly  increased — otherwise  there  will 
not  be  space  enough  for  the  condenser  to  lie  in 
without  .coming  into  dangerous  proximity  to  the 
secondary  wire.  The  sides  and  bottom  of  the  box 
should  be  dovetailed  together,  as  it  is  not  advisable 
to  use  metal  screws  near  the  coil.  The  box  may, 
or  may  not,  be  polished  ;  but,  in  either  case,  to  insure 
its  being  a  good  insulator,  it  should  be  allowed  to 
soak  for  some  time  in  melted  paraffin  wax,  previous 
to  finishing.  The  bottom  and  sides  of  the  box  being 
of  wood,  as  above  described,  the  4f-in.  square  form- 
ing the  top  cover  may  be  made  out  of  a  piece  of 
ebonite,  \  in.  or  -f  in.  thick,  cut  to  fit  squarely  on  the 
top  of  the  box,  and  nicely  polished.  Holes  will  have 
to  be  put  through  this  cover,  two  each  side,  to  enable 
it  to  be  screwed  down  to  the  box,  one  at  each  corner, 
just  clearing  the  inside  of  the  box,  to  take  the 
primary  and  secondary  terminals,  one  nearer  the 
centre  to  take  the  screw  destined  to  hold  the 
vibrating-screw  in  place,  and  a  pair  for  the  screws 
holding  down  the  brass  strap  ;  besides  this,  one 
larger  hole,  very  near  the  centre,  to  admit  the  passage 
of  a  portion  of  the  iron  core.  The  exact  position  of 
this  latter  will  depend  on  the  bulk  of  the  wound  coil 
itself,  so  that  it  may  be  left  for  perforation  until  the 
coil  has  been  placed  in  the  box. 

To  assemble  the  parts  of  the  coil  in  the  box  we 
proceed  as  follows  :  Starting  with  the  wound  coil, 
we  scrape  away  any  excrescences  of  paraffin  wax 
from  the  cylindrical  surface.  We  then  draw  out 
carefully  the  two  free  ends  of  the  primary  wire  which 
we  had  left  for  attachment,  and  having  straightened 


126    PRIMARY  AND  SECONDARY  COILS. 

them  out,  we  pass  each  one  through  a  short  piece 
of  ¥-in.  indiarubber  tubing.  In  like  manner,  using 
every  precaution  not  to  break  the  wire,  we  find  and 
straighten  out  the  free  ends  of  the  secondary  (No.  36) 
wire.  These  two  ends  should  both  be  at  the  same 
end  of  the  coil  as  that  at  which  the  primary  was 
started  and  finished.  These  wires  should  also  be  in- 
cased in  indiarubber  tubing.  Two  or  three  turns  of 
thin  (-gL  in.)  sheet  ebonite,  of  the  same  width  as  the 
wound  portion  of  the  coil,  should  now  be  wrapped 
tightly  round  the  coil,  and  fastened  thereto  by  binding 
round  with  silk  twist,  leaving  the  two  primary  and  two 
secondary  wire  ends  protruding  at  one  extremity. 
We  now  take  the  condenser,  and  by  gently  coaxing 
it  round  a  bottle  filled  with  warm  water,  cause  it  to 
take  a  semi-circular  shape,  so  as  to  fit  partially  round 
the  coil,  with  its  two  wire  ends  projecting  from  the 
same  extremity  as  the  coil  wire  ends.  We  now  place 
the  condenser  in  the  box  (see  Fig.  45),  wires  upper- 
most, keeping  it  as  far  away  from  the  centre  as 
possible.  We  then  insert  the  wound  coil,  wire  ends 
uppermost,  as  far  away  from  the  condenser  as  the 
space  in  the  box  will  allow,  but  taking  care  that  the 
entire  bobbin  stands  perfectly  upright,  with  the  centre 
of  the  iron  bundle  in  the  exact  centre  of  the  side  to 
which  it  is  nearest.  (The  iron  bundle  should  project 
about  Jin.  above  the  level  of  the  box.)  In  order  to 
retain  it  in  this  position  previous  to  the  next  step,  it 
will  be  well  to  insert  a  few  wedges  of  paraffined  paper 
between  the  coil  and  the  condenser. 

We  now  arrange  the  wires  so  that  the  primary  ends 
stand  out  as  far  as  possible  from  the  secondaries, 
especially  these  two  latter,  from  each  other,  as,  if 


PRIMARY  AND  SECONDARY  COILS.    127 

they  are  less  than  i  in.  apart,  there  will  be  a  ten- 
dency to  spark  to  each  other.  Having  seen  to  this 
important  point,  we  melt  carefully  some  clean  paraf- 
fin wax,  not  making  it  too  hot  (about  150°),  and 
pour  it  into  the  box,  so  as  to  fill  up  all  interstices  in 
the  case,  and  bring  the  surface  of  the  melted  wax 
up  to  a  J  in.  of  the  level  of  the  top  of  the  box. 


FIG.  45. 

We  can  now  make  the  f-in.  hole  in  the  ebonite 
top  or  cover  of  the  case,  into  which  the  extremity 
of  the  iron  core  will  enter,  and  allow  the  hammer  of 
the  spring  to  play  in  front  of.  By  placing  the  iron 
bob  centrally  in  this  hole,  we  shall  be  able  to  mark 
the  spot  in  the  cover  at  which  to  make  the  hole  for 
the  screw  holding  down  the  spring  and  its  little  base- 


i28  PRIMARY  AND  SECONDARY  COILS. 

block.  We  now  place  the  strap  in  position,  striding 
over  the  spring,  with  the  platinum-tipped  screw 
touching  the  centre  of  the  platinum  boss  on  the 
said  spring,  and  mark  off  and  then  drill  the  holes 
to  receive  the  screws  which  serve  to  hold  the 
strap  in  its  place.  As  it  is  not  advisable  to  use 
solder  at  any  of  these  junctions,  we  must  allow  one 
of  the  strap  screws  to  project  a  little  beyond  the 
underneath  of  the  cover,  and  fit  it  with  a  small  nut. 

The  four  terminals  are  now  inserted  near  the  four 
corners  of  the  cover.  The  two  primaries  should  be 
rather  larger,  and  of  a  different  pattern  from  those 
intended  for  the  secondary  ;  but  all  four  should  be 
fitted  with  nuts  below  to  facilitate  connections  to 
wires  without  soldering.  We  now  coil  the  ends  of 
the  secondary  wires  (previously  incased  in  indiarubber 
tubing),  each  one  respectively  round  a  small  French 
nail,  so  as  to  produce  a  neat  helix.  Withdrawing  the 
nail,  we  do  likewise  with  the  two  condenser  wires. 
(This  gives  elasticity  to  the  wire  ends,  and  allows  us 
to  manipulate  them,  and  also  to  close  the  cover  with- 
out fear  of  breaking  the  wires.)  Baring  the  ends  of 
the  secondary  wire,  and  cleaning  them  bright  with  a 
bit  of  fine  emery  cloth,  we  clench  them  under  the  nuts 
belonging  to  the  secondary  terminals.  In  like  manner 
we  connect  the  two  ends  of  the  primary  wire,  one  to 
the  nutted  screw  holding  down  the  brass  strap,  and 
the  other  to  the  nearer  large  or  primary  terminal. 
Taking  one  of  the  wires  proceeding  from  the  con- 
denser, we  bare  and  clean  it  at  about  its  centre,  and 
here  we  pass  it  under  the  nut  at  the  bottom  of  the 
screw  that  holds  down  the  vibrating  spring,  carrying 
the  remainder  to  the  other  primary  terminal,  under 


PRIMARY  AND  SECONDARY  COILS.    129 

the  nut  of  which  its  bared  and  cleaned  end  is  to  be 
firmly  clenched,  any  excess  being  cut  off  with  the 
cutting  pliers.  Lastly,  we  carry  the  other  condenser 
wire  to  the  strap  screw  where  we  had  previously  put 
the  first  end  of  the  primary  wire,  and  having  unscrewed 
the  nut,  we  twist  the  wires  together,  and  clench  them 
both  under  the  same  nut.  Care  must  be  taken  in 
making  these  connections — first,  that  the  nuts  clench 
firmly  the  wires  ;  secondly,  that  the  secondary  wires 
are  not  severed  in  tightening  up  the  nuts  ;  thirdly, 
that  the  wires  do  not  touch  or  cross  each  other  at  any 
point.  The  primary  wires  and  the  condenser  wires 
(except  only  those  two  which  are  joined  under  the 
strap  nut)  will  be  sufficiently  insulated  from  each 
other  where  near,  by  the  insertion  of  a  piece  of 
paraffined  paper.  This,  however,  is  not  the  case  with 
the  secondary  wires — these  must  be  kept  at  as  great 
a  distance  as  practicable  from  each  other,  well  covered 
in  indiarubber'tubing  ;  otherwise  leakage,  even  to  the 
point  of  sparking  across  to  each  other,  will  be  sure  to 
occur.  When  we  are  satisfied  that  this  is  the  case, 
we  cautiously  lower  the  cover,  taking  care  that  the 
wires  do  not  get  displaced,  and  screw  down  the  cover 
by  the  eight  side  screws. 

The  outlines  of  the  case  are  only  faintly  drawn  in 
the  illustration,  but  will  give  a  general  idea  of  the 
arrangement  of  the  parts  and  the  connection  of  wires. 
The  cover  is  shown  somewhat  raised. 

If  it  be  desired  to  mount  the  coil  without  the 
trembler,  and  to  depend  entirely  on  the  mechanical 
break  for  obtaining  the  spark,  the  mode  of  fitting 
up  will  be  somewhat  different.  The  case  may  take 
the  form  either  of  a  box,  as  previously  described, 

I 


130    PRIMARY  AND   SECONDARY  COILS. 

or,  as  is  often   used,  of   an   ebonite  tube  of  rather 
large   diameter,    fitted    with    flanged   ebonite  heads, 
about  -f  in.  thick  of  which  enter  into  the  tube  up  to 
flange  or  shoulder,  and  can  be  fastened   thereto  by 
three  small  lateral  screws.     No  contact-breaker  will 
be   required.     The   coil   and   the    condenser   having 
been  got  ready,  as  previously  described,  an  ebonite 
tube  of  suitable  size  to  contain   both  easily  is  ob- 
tained, of  such  a  length  as  to  contain  the  entire  coil 
and  iron  bundle   (which   in    this    case   need    not  be 
longer  than  the  wound  portion  of  the  coil)  without 
touching   the    cover.     The    primary   and    secondary 
wire  ends  having  been  drawn  out  as  directed  in  the 
last  section,  one  end  of  the  secondary  wire  is  taken 
through  a  small  hole  drilled  near  one  edge  of  the 
cover,  near  to  which  is  inserted  one  of  the  secondary 
terminals  ;  and  under  the  shank  of  this  terminal  the 
bared  and  cleaned  wire  is  clenched.     The  tube  with 
its  contained  coil  and  condenser,  is  now  turned  with 
its  open  end  uppermost,  and  the  coil  and  condenser 
being  supported  upright,  and  as  far  as  possible  from 
one  another,  melted  paraffin  wax  is  poured  in  until 
the  iron  core  is  entirely  covered,  there  being  left  pro- 
truding the  ends  of  one  secondary,  the  two  primaries, 
and  two  condenser  wires  only.     When  the  wax  has 
set   and   is  quite  hard,  the  ends  of  the  primary  wire 
nearer  the  iron  core  are  bared,  as  also  one  of  the  con- 
denser wires.     The  free   end  of  the  secondary  wire 
(which  for  this  purpose  should  have  been  so  coiled 
round  the  core  so  as  to  terminate  at  the  opposite  ex- 
tremity to  the  one  already  secured  to  the  terminal)  is 
also   bared.      Then    the    starting    extremity   of  the 
secondary  is  wrapped  round  the  finishing  end  of  the 


PRIMARY  AND  SECONDARY  COILS.     131 

primary,  and  soldered  thereto,  using  resin  only  as  a 
flux.  In  like  manner  one  of  the  condenser  wires  is 
coiled  round  the  starting  end  of  primary  and 
soldered  to  it.  The  three  ends  of  wire  are  now  each 
respectively  covered  with  indiarubber  tubing,  except 
just  at  the  extremities,  where  they  will  have  to  pass 
through  the  upper  cover  and  be  connected  to  three 
separate  terminals,  situated  at  three  equidistant 
points  near  the  circumference  of  the  cover.  The 


FlG.    46. 


MB 


cover  should  now  be  fastened  in  its  place  by  three 
short  lateral  screws  passing  through  the  tube.  The 
terminal  to  which  the  single  condenser  wire  is  con- 
nected should  be  marked  K  (see  Fig.  46) ;  the  solitary 
terminal  to  which  the  single  (or  finishing)  secondary 
wire  was  carried  at  the  back  end  of  the  coil  should 
be  marked  S  +.  In  like  manner  the  terminal  to 
which  the  joined  secondary  and  primary  are  con- 
nected may  be  marked  A ;  while  the  one  making  con 


1 32     PRIMARY  AND  SECONDARY  COILS. 

nection  to  the  conjoined  primary  and  condenser  wires 
will  receive  the  mark  B. 

As  it  is  essential  to  the  proper  working  of  the  coil 
that  the  terminal  S  +  should  be  in  a  positive  state 
when  the  coil  is  connected  to  its  battery  or  accumu- 
lator, and  as  its  condition  will  vary  according  to 
which  pole  of  the  battery  is  connected  up  to  B  and  K 
respectively,  it  will  be  advisable  to  test  this,  and  mark 
one  of  these  terminals  with  +  when  found.  This  is 
easily  done  by  connecting  up  the  battery  to  A  and  K, 
first  in  the  one  direction  and  then  in  the  other,  an 
assistant  in  the  meantime  rapidly  making  and  break- 
ing contact  with  a  piece  of  wire  between  K  and  B,  the 
operator,  not  the  assistant,  holding  at  the  same  time 
his  knuckle  at  about  \  in.  from  S  +.  When  the 
proper  poles  of  the  battery  are  being  used,  a  fairly 
strong  spark  will  pass  from  S  +  to  the  operator  ; 
but  if  the  battery  is  wrongly  connected,  there  will  be 
either  none  at  all  or  else  a  very  faint  one.  In  per- 
forming this  trial  the  operator  should  be  careful  not 
to  come  into  contact  with  his  assistant,  otherwise 
they  will  both  receive  a  pretty  sharp  shock  ;  and  the 
assistant  must  be  careful  not  to  leave  the  testing  wire 
in  contact  with  both  terminals  K  and  B  for  any 
appreciable  length  of  time,  but  simply  to  flash  it 
across  the  two  ;  otherwise  he  will  heat  the  wire  and 
run  down  the  battery.  In  using  such  a  coil  the 
terminal  S  +  is  taken  to  the  ignition  plug  of  the 
motor,  the  cell  connected  by  its  proper  poles  to  A  and 
K;  while  two  separate  wires  connect  K  to  the  spring 
of  the  mechanical  break  (M  B),  and  B  to  the  body  of 
the  engine  respectively. 


INDEX, 


PACK 

ACCUMULATOR  34,52,95 

Action  of  secondary  coil         104 

Advancing  ignition      ...         ...         ...         ...         ...  14,  97 

^Etna  lamp         ...         ...         ...         ...         ...         ...         ...       50 

Air  valve,  automatic 19 

Alcohol  as  fuel 44 

Alternators,  useless      ...         ...         ...         ...         ...         ...       61 

Ampere  ...         ...         ...         ...         ...         ...         ...         ...       90 

Annealing  iron 92,106,111 

Armature  58,63,73,82 

Assembling  coil  parts 125 

Automatic  cut-out  for  oil         41 

„  „  dynamo  53 

„         governor     ...         ...         ...         ...         ...         ...       18 

„         lubrication 14,  39 

„         valves          ii,  19 

„         interrupter...         ...         ...         ...         ...         ...       85 

B 

"  BACKLASH  "  effect     no 

"Bain  Marie" 109 

Balance  gear      ...         ...         ...         ...         ...         ...         ...       23 

Bare  copper  wire          ...         ...         ...         ...         ...         ...     109 

Bassee  Michel  magneto          ...  ...       64 

Battery  for  coil 52 

Bell  crank  lever  11,  80 

Belts        ...       19 

Binding  of  engine        ..         14 

Brake      ...  ...  33,  38 

„     bands        34 


134  INDEX. 

PAGE 

Brass  segment 14 

Breaking  contact          78,  84,  89,  1 06 

Breguet's  igniter  56 

Brush      14,61 

c 

CAM        n,45 

„     exhaust-valve       n,45 

„     half-speed 15 

Carbon  pencil...  80 

Carburetter        14 

„          for  paraffin  44 

„  surface      ...         ...         ...         ...         ...         ...       15 

Cardan  joint      23 

Car,  selection  of  ...         ...         ...         ...         ...         ...       40 

Case  for  coil      124 

Chain      19 

Chassis 25 

Choice  of  car     ...         ...         ...         ...         ...         ...         ...  9,  40 

Clapper,  or  hammer 123 

Clutch 19,21 

Coils        88,  103 

„     case  for      124 

„     current  needed     ...         ...         ...         ...         ...         ...       90 

„     (dynamo) 66 

„     heads         92 

„     making      ...       92 

„     primary,  how  to  make 92 

„     with  trembler       110,129 

Combustion  chamber n 

Commutator      61,65,69 

Compound  dynamos    ...         ...         ...         ...         ...         ...       53 

Condenser          64,69,83,107,116,120 

Connecting  rod...         ...         ...         ...         ...         ...         ...       u 

Connections       77,  80,  128-132 

Contact  breaker  64,72,82,106,122 

„        breaking  and  making          68,  78,  84,  89,  92 

„        spring 74»  85,  122 


INDEX.  135 

PAGE 

Controlling  dynamo     ...         ...         ...         ...         ...         ...  56 

Copper  plug       ...         ...         ...         ...         ...         ...         ...  80 

Core,  making 91,104,110 

„     soft  iron 91,  104 

Crank,  starting 35 

„       chamber            11 

,,             ,,         covers           ...         ...         ...         ...         ...  n 

,,       shaft       ii 

Currents,  extra 89 

„         induced          89 

„         path  of           80 

.,         primary          88 

,,         secondary      ...         ...         ...         ...         ...         ...  88 

,,         self-induction             ...         ...         ...         ...         ...  89 

Cycle  of  operations      34 

Cylinder ...  n 

cover  ...                                            ...                     ...  ii 


D 

DAMPING  effect  90 

Dead  point        97 

Differential  gear  23,26 

„  „      hints  on       38 

Distributor         72,82 

Driving  a  car 34 

„        or  starting  handle      35 

Dynamo  53,  61 

„         alternator       53,  61 

„         coil      66 

.,         controlling 56 

,,         compound      ...         ...         ...         ...         ...         ...       53 

Elbridge         65 

„         essentials  of 53 

„         inclosed          54 

open    ...  ...       54 

„         series ...       53 

suitable          55 


INDEX. 


PAGE 

EARTHING        77, 80 

Ebonite  heads  ...         ...         ...         ...         ...         ...         ...     109 

„       sheet 109 

»       tube      ...  94,  113 

Eisemann  magneto      70 

Elbridge  igniter  ...         ...         ...         ...         ...         ...       65 

Electric  circuit  ...         ...         ...         ...         ...         ...         ...       14 

„        current,  how  set  up 57 

E.M.F.    ...  ...  ...  34,57 

Engine,  paraffin  ...         ...         ...         ...         ...         ...       42 

„        Parsons'  42 

„        position  of      41 

Exhaust  gases   ...         ...         ...         ...         ...         ...         ...       32 

„         valve    ...  ...  ii,  44 

Expanding  clutch         34 

Explosion,  wrongly  timed       ...         ...         ...         ...         ...       97 

Explosive  mixture        14,  18 

"Extra"  current  89 

F 

FAN        15 

Fibre  disc  ...         ...         ...         ...         ...         ...         ...       14 

Field  magnets 64,67,71,86 

Filter  for  petrol  ...         ...         ...         ...         ...         ...       34 

Firing  or  ignition  plug  ...    14,80,100 

„      spark       ...  14,95 

Flooding  the  carburetter         ...         ...         ...         ...         ...       35 

Fly-wheel  10,  21 

Foot  brake         33 

Friction  clutch 19 

G 

GAS-TIGHT  fit 11 

Gear,  balance 23 

.^     differential          23,  27 

„     three-speed         22 


INDEX.  137 

PAGE 

Gear,  wheels      11,22,40 

Gianoli  magneto  83 

Governor,  automatic 18 

Graphite  40 


H 

HALF-SPEED  cam        n345 

Handle  for  starting      35 

Hammer  or  clapper     123 

Heat  dissipation  ^5  29 

Heating  in  dynamo      55 

Helicoidal  lock-nuts 40 

Helix       8.9 

High-tension  magneto  ...         ...         ...  69,  70,  81,  83 

Hints  for  drivers  38 

How  to  make  a  primary  coil 92 

„         „         secondary  coil          ...         ...         ...         ...     no 


I 

IGNITION 49 

„         advancing     ...  37,  76,  97 

„         Bassde-Michel         64 

„        Bseguet's      56 

„        by  coil  , ...  71 

„        by  dynamo  coil       ...         ...         ...         ...         ...  66 

„        by  flame        ...         ...         ...         ...         ...         ...  5° 

„        by  magneto  ...         ...         ...         ...         ...         ...  70 

„         by  platinum  ...         ...         ...         ...         ...  50 

„         Crossley's     50 

,,        Eisemann     ...         ...         ...         ...         ...         ...  7° 

„         Elbridge       65 

„         Gianolo         ...  83 

„         Lenoir's        ...  49 

„         Otto  and  Langen;s  ...         ., 50 

plug   ...  ...  ...     14,  80,  100 

„        Priestman's 50 


138  INDEX. 

PAGE 

Ignition,  retarding       37,76,97 

„       Simms-Bosch  63,  81 

„       timing,  important 96 

,,        Torrens'          ...         ...         ...         ...         ...         ...     100 

Induction  coil 88,  103 

Inlet  valve         u 

Insulation  108,  113 

Interchangeability        40 

Ironclad  dynamo          ...         ...         ...         ...         ...         ...-      54 

Iron  core  91,104,110 

L 

LAMP,  "yEtna"  or  "Primus"           50 

Launch  Engines           41 

Levers,  for  control        21 

Lines  of  force 57 

Lock-nuts           ...         ...         ...         ...         ...         ...         ...  40 

Low-tension  magneto 64 

Lubrication        38 

Lubricating  oil 39 

Lubricator          14 

M 

MACHINERY,  accessible         '       ...      40 

Magnetic  field 59 

Magneto  ...    56,63,64,65,66,69,70,81,83 

Making  contact  78,89 

Motorcars         9 

„      proper 10 

„      paraffin 42 

„      Parsons'  42 

N 

NEGATIVE  wire  59,81,98,99 

Neutralizing  paraffin  by  chalk  108 

Neutral  position  of  gear         22 


INDEX.  139 

^  PAGE 

OIL  ...        39 

One-inch  spark  coil      ...         ...         ...         ...         ...         ...     no 

Otto  engine        50 

P 

PACKING  rings 11 

Paper,  paraffined          94 

Paraffin  as  fuel 42 

Paraffining  paper          ...         ...         ...         ...         ...         108,  116 

Parsons' engine             42 

Petrol  motor      10 

»      required 34 

„      tank        ...  ...  ...  29,  34 

„      vapour 14 

Pinion     ...         ...         ...         ...          ...         ...         ...         ...  11 

Piston      ii 

Platinum  points             80 

Plumbago          ...         ...         ...         ...         ...         ...         ...  40 

Positive  or  "live"  wire  59,81,98,99 

Power,  transmission  of           19 

Primary 88 

„       coil    f 88,  92 

,,          ,,    Torrens'   ...         ...         ...         ...         ...         ...  100 

„       winding            ...                                            93 

Pump,  oil            14 

„      water      15 

Push-rod            ii 

R 

RADIATOR        15, 29 

Rectified  currents         ...         ...         ...         ...         ...         ...       61 

Retarding  ignition        37,  76,  97 

Revolutions  per  minute  41 

Ribs         41 

Rings  for  packing         ii 

Rod,  piston        ii 

„     push  ii 

Ruhmkorff  coil 104 


14°  INDEX. 

s 

PAGE 

SAFETY  spark  gap       83 

Secondary  coils  88,103 

„          coil,  making          no 

„          currents      89 

„          winding      n4 

Seizing  of  engine          14 

Self-induction  current 89 

Series  dynamo 53 

Shield      82 

Shunt  dynamo  ...         ...         ...         ...         ...         ...         ...       53 

Silencer !4?  32 

Simms-Bosch  igniter 63,81 

Sleeve i4j  82 

Softening  steel 122 

Solid  lubricants  39 

Sparking  coil  (see  Coils}          

,;        plug 14,  80,  100 

Spark  timing     14,  97 

Spray,  carburetter        15 

Spring,  softening          ...         ...         ...         ...         ...         ...     122 

„       tempering        123 

Springs,  valve n 

Sprocket  wheel 23 

Starting  handle  ...         ...         ...         ...         ...         ...       35 

Stationary  engines       41 

Steering  gear 26,28 

Suction    ...         ...         ...         ...         ...         ...         ...         ...       ii 

Surface  carburetter      15 

T 

TANK,  petrol     29,34 

,,       water      ...         ...         ...         ...         ...         ...         ...       29 

Tempering  spring         123 

Testing  coil        95 

Testing  for  correct  connections         132 

Throttle-valve   .  18 


INDEX.  1 4  I 

PAGE 

Timing  the  spark         14,85,97 

„       disc       ...  74,  84 

Torrens'  sparking  plug  ...         ...         ...         ...         ...     100 

Transmission  of  power  19 

Trapeze  rod       98 

Trembler  coil     ...         ...         ...         ...         ...  106,  no,  129 

Tube,  ebonite 94,  113 


V 

VALVE,  automatic        u 

„       box       ii 

„       exhaust            11 

,,       inlet      ii 

Valves ii 

Vapour,  proportions  of            18 

Vulcanised  fibre            14 

w 

WARMING  petrol         44 

Water-cooling u 

„      jacket ii 

„      tank       29 

Winder 112,  114 

Winding  the  primary 93 

„         „    secondary          ...     114 

Wiping  contact  88,  96 

Wire  for  coils 93,112,115 

,,      „   cores 92>  II0 

,,     negative  and  positive 59,  Si,  98,  99 

Wiring 77,  80 


HANDICRAFT  SERIES  (Continued). 


Photographic  Studios  and  Dark  Rooms.     With  180  Illustrations. 

Contents.— Planning  Studios.  Building  Studios.  Portable  and  Temporary  Studios. 
Studios  Improvised  from  Greenhouses,  Dwelling  Rooms,  etc.  Lighting  of  Studios. 
Backgrounds.  Scenic  Accessories.  Dark-Rooms.  Portable  Dark-Rooms.  Dark-Room 
Fittings.  Portable  Dark  Tent.  Index. 

Motor  Bicycle  Building.     With  137  Illustrations  and  Diagrams. 

Contents. — Frame  for  Motor  Bicycle.  Patterns  for  Frame  Castings.  Building  Frame 
from  Castings.  Making  3£  H.  P.  Petrol  Motor.  Spray  Carburettor  for  3£  H.  P.  Motor. 


Ignition  Coils  for  Motor  Cycles.     Light-weight  Petrol  Motor  for  Attachment  to  Roadster 
Bicycle.     Spray  Carburettor  for  Light-weight  Motor.     Index. 

Rustic  Carpentry.     With  172  Illustrations. 

Contents.— Light  Rustic  Work,  Flower  Stands,  Vases,  etc.  Tables,  Chairs  and  Seats. 
Gates  and  Fences.  Rosery  Work,  Porch,  Swing  Canopy  Aviary,  Footbridges,  Verandahs, 
Tool  Houses,  Garden  Shelters,  etc.  Summer  Houses,  Dovecot.  Index. 

Pumps  and  Rams  :     Their  Action  and  Construction.     With  171  Illustrations. 

Contents. — Suction  Pumps  and  Lift  Pumps.  Making  Simple  Suction  Pumps,  Pump  Cup 
Leathers,  Pump  Valves,  Ram  or  Plunger  Pumps.  Making  Bucket  and  Plunger  Pump. 
Construction  of  Plumbers'  Force  Pump,  Wooden  Pumps,  Small  Pumps  for  Special 
Purposes,  Centrifugal  Pumps.  Air  Lift,  Mammoth,  and  Pulsometer  Pumps,  Hydraulic 
Rams.  Index. 

Domestic  Jobbing.     With  107  Illustrations. 

Contents. — Cutlery  Grinding,  Sharpening  and  Repairing.  Simple  Soldering  and  Brazing. 
China  Riveting  and  Repairing.  Chair  Caning,  Furniture  Repairing,  Glazing  Windows, 
Umbrella  Making  and  Repairing.  Index. 

Tinplate  Work.    With  280  Illustrations  and  Diagrams. 

Contents. — Tinmen's  Tools,  Appliances  and  Materials.  Elementary  Examples  in  Tin- 
plate.  Hollowing  Tinplate.  Simple  Round  Articles  in  Tinplate.  Saucepan  Making. 
Square  and  Oval  Kettle  Making.  Oil  Cooking  Stove.  Set  of  Workshop  Oil  Cans.  Fancy 
Paste  Cutters.  Lamps  and  Lanterns.  Index. 

Other  Volumes  in  Preparation. 

DAVID  McKAY,  Publisher,  Washington  Square,  Philadelphia. 


14  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 

LOAN  DEPT. 


RENEWALS  ONLY—TEL.  NO.  642-3405                     )  N  . 
Imp      This  book  is  due  on  the  last  date  stamped  below,  or      |N.  HAS  LUCK 
on  the  date  to  which  renewed. 
Renewed  books  are  subject  to  immediate  recall.          about  l6°  Pages> 

/:    JAN     21970 

* 

d's    Instruments. 

Back 

Prac              *— 

Co 
/-i 

ves.     Projection. 

ifti/  "^     fi?i^   A  fill       ings-  Making  a 

JMH  /  ^    /V  "^tPiW 

the  Gas  Holder. 

Mete: 
Gas  I 

the  House.     Gas 
ps  and  Theatres. 
Index 

Prac 

Coi 

kircase  —  Housed 

with 
Half-; 

base.      Staircase 
Staircase  with 
th  Open    or    Cut, 

String 
Step. 

Praci 

s  with  Bull-nose 
i.     Index. 

Con 
Figure 

uction  of  Plane 
res.     Tools    and 

Applu 
and  G 
Pattei 

ig.     Re-tinning, 
les  of  Practical 

Pract 

Com 

ining  Grounds 

Pollan 
Grainii 

Water  Colours, 
and  Pitch-pine 
nff.      Imitating 

Woods 
Materi; 

Painff 

on,   Tools,  and 

Contt 
Chroni( 

s. 
Blue  Pigments, 
•own  and  Black 

Mixing. 
Prantl 

t  Grinding  and 
Index. 

. 

Contt         T  TVOI  A    ct\     a  >«n                                   General  Library                    ,  T      j  -r^r    •, 
LD21A-60m-6,'69                              University  of  California          >et  Lead  W  ork- 
**&     T         (J9096slO)476-A-32                                    Berkeley                       *.    Index. 

Practi^ 

Contents.— -Foundry  Patterns  and  Foundry  Practice.  Jointing-up  Patterns.  Finishing 
Patterns.  Circular  Patterns  Making  Core-Boxes.  Coring  Holes  in  Castings.  Patterns 
and  Moulds  for  Iron  Columns.  Steam-Engine  Cylinder  Patterns  and  Core-Boxes.  Worm 
Wheel  Pattern.  Lathe-bed  Patterns.  Headstock  and  Poppet  Patterns.  Slide-rest 
Patterns.  Miscellaneous  Patterns  and  Core-boxes.  Index. 


TECHNICAL  INSTRUCTION  (Continued}. 

:al  Handrailing.     With  144  Illustrations. 

^te. — Principles  of  Handrailing.  Definition  of  Terms.  Geometrical  Drawing. 
Handrails.  Wreathed  Handrails  on  the  Cylindrical  System.  The  Uses  of  Models, 
ig  Tangents  and  Bevels.  Face  Moulds:  their  Construction  and  Use.  Twisting 
ath.  Completing  the  Handrail.  Orthogonal  or  Right-angle  System  of  Setting 
id  Handrails.  Handrails  for  Stone  Stairs.  Setting  out  Scrolls  for  Handrails, 
out  Moulded  Caps.  Intersecting  Handrails  without  Basements.  Index. 
•al  Brickwork.  With  368  Illustrations. 

its. — English  and  Flemish  Bonds.  Garden  and  Boundary  Walls.  Bonds  for 
Angles.  Excavations,  Foundations,  and  Footings.  Junctions  of  Cross  Walls. 
Piers.  Angles  and  other  Bonds.  Jointing  and  Pointing.  Damp-proof  Courses 
struction.  Hollow  or  Cavity.  Walls.  "  Chimneys  and  •  Fireplaces.  Gauged  Work 
bes.  Niches  and  Domes.  Oriel  Windows. 
al  Painters'  Work.  With  Numerous  Illustrations. 

its. — Objects,  Principles  and   Processes  of  Painting.     Painters'  Tools  and  Appli- 
Materials  us«dhv  Paints ra      Po^t    AT:-: —        T>_—  •      -  ~   ;nting> 

jering 
Stains 


267484- 


vtions. 


iching 


and 
acene 
ithod 
adex. 


••tion. 
oors, 


>ns. 
Ores 


tewas. 
ning. 
Fabi 

its.— ( 
leachi 
^ater. 

g  Ma 
Us.— 1 
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Matt 
ing  Ej 
y  Co 
its.— I 
5,  Fou 
,  and 
Its  S 
its.— I 

Met 

S  in  the  UIast  Jb'urnace.  l^last  Furnace.  Air  Supply.  Blowing  Engines 
;  the  Blast  Furnace.  By-products.  Malleable  or  Wrought  Iron.  Production  of 
ie  Iron.  Preparation  of  Malleable  Iron  in  Open  Hearths.  Puddling.  Refining 
i  and  Dry  Puddling.  Forge  Machinery.  Iron-rolling  Mill.  Index. 
Its  Varieties,  Properties,  and  Manufacture.  With  132  Engravings  and 
grams.  By  WILLIAM  HEN*?  '  GREENWOOD.  Revised  and  Rewritten  by  A. 
MBOLDT  SEXTON.  "  * 

its.— Steel:    Its  Properties  and  Manufacture.     The  Bessemer  Process.     The  Basic 
r   Process.      Modifications  of   the    Bessemer    Process.      Gas    Producers    and    the 

Furnace.  The  Siemens  or  Open-hearth  Steel  Process.  The  Basic  Open-hearth 
Modifications  of  the  Open-hearth  Process.  Steel  Works  Appliances.  The 
,tion  and  Monor  Steel  Processes.  Casting  Steel.  Forging  and  Rolling  Steel, 
•pic  Structure  of  Steel.  Heat  Treatment  of  Steel.  Theory  of  Steel.  Testing 
Specifications  of  Steel  for  Various  Purposes.  Alloy  Steels.  Index. 

Other  New  Volumes  in  Preparation. 
DAVID  McKAY,  Publisher,  Washington  Square,  Philadelphia. 


UNIVERSITY  OF  CAL^OEJ^  LIBRARY ^ 


